Indeed, many applications I would expect to prevent sleeping (some audio playback ones, games, etc.) don't implement this. I assume it's a case of Apple's APIs changing over the years and not everyone catching up/caring. At one point I had downloaded Amphetamine[^1] but it is much nicer to just use the terminal here.
[^1]: https://apps.apple.com/us/app/amphetamine/id937984704