Same as with any other requirement: when you can afford it.
Slack's desktop client shouldn't require Electron (making it unusable on low-end devices), but it does. They can get away with that requirement, because there's hardly any alternative client worth your effort/attention.
I was sceptical about BitWarden (versus 1Password), because their UX was quite far behind - but they're slowly catching up, and I might have to reconsider my choice there.
If I wasn't "required" to run a dozen different proprietary/non-portable apps, I'd be using OpenBSD instead of macOS.
I do not "require" X to be free, but given all other things being equal, it's my preferred choice. Unfortunately, a lot of the time, we do not have the luxury of being picky.