The problem I think with NOT eating together is that it sews disharmony in the machinery of the household.
If everyone DOES eat together all the work related to it happens together as somewhat of a team. You do the thing once. Everyone is in a shared state of being. Specifically being satisfied in appetite and social interaction and ready to do there own thing after.
Otherwise Billy is hungry at a different time than Sandy and Sara wasn't hungry until it was time for bed. Dishes have to be re done for each person. Billy made a better dinner for himself and left none for his sister. Someone ate in the bedroom and left a glass of milk out over night and mom was angry in the morning...
I am rambling and maybe it's obvious but ultimately I don't think it's just the act of eating together I think it's the reduced friction and increased cohesion of the household that shared dinner causes.
To answer your question, Maybe family dinner forces you to be "doing it right" just by the act of having the family dinner.
That's not to say you can't screw it up. If family dinners are spent in silence with the kids praying they get through the dinner without setting dad off again and watching him beat their mom to a pulp, or hoping that they don't get sexually abused later that night by one of their family members, etc. Then yes, maybe there are some quality issues, but I'd argue even in that extreme case, it might still be a positive indicator against the base cases of abuse without that element.
I was a paramedic. There is a massive fraction of society with upbringings like you wouldn't imagine. That's what you're up against. When people say they have a dysfunctional family, it's often pretty mundane. Especially compared to people in that class that didn't realize until they were an adult that things like getting raped by all of their mom's boyfriend's isn't a normal thing everyone deals with as soon as they start puberty.
I've done it all my life, as a child and a parent, I have no idea why people would not want to enforce this.
IMO, having regular family dinners is just one of many characteristics of stable and healthy families.
As you have more meals together, you are (they bond to you) and feel (you bond to them) more loved by the other people at the table.