They said they use it, just not much.

And given that it was a non-pricy one-time purchase, and not a subscription, why would they regret it? The cost per hour of usage is only going to keep decreasing over time for them, as long as they keep using it in some capacity occasionally.

Because I was using it to practice making digital art which I just don’t have time for right now. I use it to make Christmas cards and doodle probably 5x in a year.

I don’t regret it because I can see that what I paid for is worth the value of the app despite not using it as much.

It's like $5. Even if you don't use it, you can tell it's a great app, updated often for free, etc. I've regretted apps I've paid $5 and $10 for and were crap, or baited me and turned to subscriptions etc. Procreate is not that.

Why do you need to regret spending money if you don't use what you spent it on?