Why is it so hard to send a correct UserAgent?

Especially with the rush from Twitter, there are more and more bots and crawlers coming up from the Fediverse that just can't manage to send a correct UserAgent.Many apps, which want to make usage of several platforms, just submit the framework they use for their connection. Like python/1.2.3, Dart/1.23 or http.rb/1.2.3.The biggest problem with this behavior is, that I as the operator and administrator want to secure the system, but I would lock out legitimate software by targeting only the UserAgent. Especially the python/1.2.3 in particular, but has also attracted malicious attention many times in my log files.I'm really grateful, that Lemmy developer decided to use a customized UserAgent, so that I as admin can directly see what request it is and where it comes from. That makes it so much easier to make the decision of harm or no harm.On my servers, I started to block all requests with a “default” or empty UserAgent, but I wonder, how it's possible to fix this issue in general? Any ideas?