Having flown in VATSIM towered air space and airports it is some of the best VR flight sim time I ever had.
Had someone on ground and tower at KPAO and several of us pilots were just flying the pattern and it was a blast. Not to mention one was a licensed pilot based out of there who gave me IRL tips for my lesson that week about the field which were really helpful.
I suspect popularity of sims like this is because of people who cannot be candidates for ATC roles - either have family or lifestyle restrictions that prevent them relocating or doing shift work, drug dependencies or medical issues, or criminal backgrounds.
Of the controllers I have chatted with while they stream on twitch this is the answer. Many people don't realize the controllers have medical tests as well.
The biggest one tends to be that they are simply too old, or have retired already. The retirement age is 56, with effectively no exceptions.
Virtually nobody lasts that long. If they don't end up needing a prescription that disqualifies them before 50, they end up getting incentivized to leave at 50 anyways.
I feel like those folks would already have been candidates for air traffic controller jobs though.