Comment by usef-

The selling feature is that it's more polished (and has good accessibility etc), they're still intended to be customised, which you could use AI for. Why use Tailwind itself when you could generate one with AI? Because it's solidly tested and polished, similarly.

But the broader, more important point: an open source project previously could be funded by using attention to sell other services or add-ons. But that model might be gone if users no longer visit or know the creators.