Most people mention the costs of owning aircraft vs a sim, but there's another possible reason: health. People come in different shapes and forms and not everyone who loves aviation is able to get II or even III medical class. So flight simulation is their only option to be a "pilot".
I mean, on VATSIM (popular aviation simulation network) there's a group of visually impaired people who have made a special interface so they can fly an aircraft even though they can't see!
Simulation (of any kind) gives many people what they can't get in any other way. And as with any other hobby, as long as it's not damaging to other aspects of your life, let people enjoy what they want
This doesn't sound like a lot, until you consider it was the #2 most dangerous occupation in the US that year.
Behind #1 Loggers (111 per 100k) and ahead of #22 Police Officers (14 per 100k).
So it's one thing to have a flight sim rig and at worst fall off your chair.
A whole another thing to potentially make a mistake in an actual plane and pay the price with your life.