Building Unearthed Arcana Characters?

Why can we not use Beyond to build Unearthed Arcana Characters? They can always put a tag in the Class or Subclass that allowed them to deactivate or delete it once the test was over. I have three active Campaigns and three groups of weekly pickup games available to me and exactly zero want to make characters outside of Beyond. Why offer a product that allows players to quickly build characters, hold their hand through the process that explains in detail what the class or subclass can do, ensure they have the confidence to play it, and then limit it to paper only?

What am I missing here? I don't have the time to make custom builds for everyone. Doesn't it innately limit the sample size to mostly people who have not actually played the class/subclass but instead "just vibes?"

They used to do this, years ago. They stopped because it was costing a lot of time and money to implement playtest material that often changed radically before publication, or even ended up never getting published at all. It wasn't worth the spend from their perspective.