To make it sustainable. That's about the only reason, which given the recent TailwindCSS stories, isn't necessarily a bad reason.

>”To make it sustainable”

That’s a flimsy argument. Product sales can do that. Doesn’t need to be a subscription unless you know your market is weak or your data mining.

We can’t be ok with everything being a subscription. You won’t have any money left or, worse, only the rich can afford the tools. I’m much happier paying for $60 Steam games and forgetting about them after a month. Sell this for $20 forever and do it 50,000 times by building a good product. If you get to market mass where you need a dev team to keep up with all the bleeding edge changes to SQL that are coming out, then charge a subscription.