A requirement like that incentivizes people to find a way to work around it and requires enforcers to be able to prove someone did indeed own X percent. It also

A requirement like that incentivizes people to find a way to work around it and requires enforcers to be able to prove someone did indeed own X percent. It also makes it harder to pursue cabals that collectively corner a market without any entity involved being over the threshold. In many ways, it's easier enforcement-wise to just ban the thing, especially if you don't think it's actually important to have in the first place.