In the city I grew up in, there’s a Chinese restaurant near my home that never gets packed, not even on busy weekends. I’ve also never seen more than 2 customers at a time eating there. And yet, it’s outlasted every single restaurant in the vicinity for 3 decades. That, and there’s always an expensive car or two parked in front.
The menu isn’t crazy expensive (for the area), but not like dirt cheap, too. You’re probably right that it might be their home so they can get by without much customers.