Parking minimums of any kinds are problematic when based off of some ostensible causal relationship with land use. Bike parking minimums set in this way are especially arbitrary.
Although they pale in comparison with the standards developed for automobiles, a range of cities across the country have minimum parking requirements for bikes. Similar to standards for motor vehicles, these rules usually say that for every x square footage of each type of activity (land use), you need a certain number of bike parking spaces, either short term (a rack outside) or long term (a bike cage, storage room, locker, or similar). As a regulation, these look about the same as car parking, but they are about as similar as sharks and a dolphins--they look similar but are fundamentally different. They are the same type of regulation attempting to solve two completely different problems.
The intent of car parking minimums is usually an attempt to prevent traffic congestion on adjacent streets (which they ultimately fail to do), while the intent of bike parking minimums is usually to encourage biking (which they can help with). Car parking minimums are fundamentally 'harm-reducing'--trying to somehow prevent people from parking on the free public street--while bike parking minimums are 'benefit-seeking'--trying to encourage people to ride their bike and park it somewhere. Because these two types of regulations are fundamentally different in intent, you would expect that they wouldn't be designed and measured within the same framework, but that's exactly what happens.
Vehicle parking requirements are usually set based on decades of observations in environments designed for driving. Although they are okay for predicting driving behavior in that type of environment, they don't provide much useful information about how people travel in other circumstances. It's like gathering information on cattle moving inside a corral--it doesn't tell you how cattle move, but how cattle move in spaces designed to make them move a certain way. However, once you have millions and millions of corrals you can constantly refine your observations about cattle behavior within them, and so you'll probably be pretty good at perpetuating the same system.
Bicycle parking requirements can't work that way because there aren't really any cities which have spent 70+ years mandating bike parking and building bike infrastructure. As a result, bike parking minimums are usually set based off of what other cities have done, which was probably some random fraction of their vehicle parking requirements (which are mostly arbitrary in their own way). This is problematic because biking behavior in Minneapolis is probably a lot different from biking behavior in Phoenix--and not only because of the weather, but because of the different amount of infrastructure--bike lanes, existing bike parking, local traffic laws, et cetera. The status quo approach doesn't consider this basically because it's more complicated and expensive to look for real causal information than to just copy existing vehicle parking standards. This goes back to the problem of seeking easy answers that has plagued transporation planning since the 1960s:
"...Land use is perhaps the more convenient measure...because it enables travel to be related to a tangible, and relatively predictable quality. However, it must be thoroughly understood that people make trips, and that land use is only a convenient indirect measure of the type and geographic location of trips made."
Public planners could be lazy, beleaguered, afraid of busybodies, or maybe just unaware--so they go with the easiest solution that is politically palatable.
So how should cities set bike parking minimums? I think the first thing to emphasize is that when a city sets any sort of vehicle storage minimum, they aren't "accommodating demand", they are "encouraging demand by _______ mode of travel." Parking minimums are an explicit policy choice to encourage a certain type of travel behavior. Bike standards should be required if your community wants to encourage biking. Car standards should be required if your community wants to encourage driving. That cities (like Portland, shown in this image) imagine that bike standards are just to encourage biking but car standards are a response to some organic need shows how muddled all of the thinking is around transportation in general. The way to go about setting any vehicle minimums is start from the position that they are all aspirational--they're just whatever your community wants them to be. Do you want more biking in your town? Then require 50 bike parking spaces at the super market. Do you want more driving? Then require the usual 300 or whatever. Square footage of a grocery store or bowling alley or office does not determine how much people ride or bike--what's in the infrastructure around them does. Except for what's in the right-of-way, there isn't really much of causal link between land use and travel.
To conclude, I recently was involved in a project setting bike parking minimums in a medium-sized city. It was a long fight for what were barely even noticeable standards. Seeking to set them on some sort of objective data, we generally required a single u-rack for every use, and then settled on requiring a certain number of bike racks based on the percentage of city commuters that were cyclists multiplied by the number of employees or expected visitors. This is a real data relationship, and would presumably serve the needs of all the people who are already biking but currently have no place to lock up (nevermind all the people who would bike more as soon as more infrastructure became available). Even this, however, got some pushback, when other planners in the room insisted that it's too hard to count employees or trips so we had to somehow tie it to land use--again going back to picking what is easy rather than what is correct. On this point we negotiated using average square footages available per employee by land use according to the US Energy Information Administration data --not ideal, but significantly less embarrassing than trying to straight-face the idea that "land uses generate trips" the way that engineers think they do with cars.