because someone might have a use for them.
also the “beta” is not officially supported anyway. sometimes we have plugins there because they just come from a bigger collection of plugins. it is quite some work to try all plugins in a big collection to see which ones are okay and which are not… so uploading the whole thing it is, because out of 6 bad ones there might be a gem.
this is just my opinion though. and again, the “beta” plugins are not officially supported.
another thing to consider (this is just an example) is that it gives us a nice overview of what is possible. there might be a beta plugin that is very good, but crashes if we do X or Y. while not usable, it already tells us there is a great plugin available if we fix the crashes.
back when we published all these plugins to the store, we could not predict which ones would be good and which ones “bad”. so we uploaded them all behind an advanced-user-mode-only filter. then slowly moved plugins out of “beta” into “stable”.