Very strict standards would become political very quickly and lead to conflict. There is a huge difference of opinion about what constitutes tidy and weed free. My plot has stinging nettles on it. They are a useful habit that attracts beneficial insects. I let the grass grow longer as a habitat for frogs. I don't use chemicals on bind weed just pull it out. My shed leans over a little and needs painting. It looks a bit of a mess sometimes but is actually fairly well cared for. But some people won't see it like that. The wonderful thing about an allotment is that it is a space to play a bit without too many rules. And a more relaxed approach to care is more sustainable in terms of effort.

I initially considered that... But then you can just pay someone to meet the standard, and keep the allotment forever.

It effectively becomes land you own permanently. And the price would probably go from 'a few hundred bucks for something that will entertain me for a year' to 'an investment that will rise in value and I can give my children, so $400k'.

Knowing that a fixed percentage of owners will be stripped of their holding each year makes it a very unattractive investment, while not preventing most of the other uses of an allotment.