Depends on how big the group is. I don't mind eating at 9pm if it's just me and dh or a couple of friends.
If it's a larger group, there increases the risk of Faffers who don't even look at the menu before they've had a chance to catch up with everyone, go to the toilet, nip out for a cig, have a drink....then when their attention turns to the menu they read every item carefully and offer it up for discussion.
They will have the steak, but don't want X accompaniment and want a side of onion rings but don't think they will eat a full portion of onion rings, who wants to share a side of onion rings with them? Ah that's three people, best get two sides of onion rings then. Actually, on reflection they'll have the salmon. It says seasonal veg on here, does anyone know what veg they actually serve it with? I'll go ask. Hmm, not keen on brocolli. Ok, il have the steak.
And then when the waiter arrives to take the order, they look surprised and start hemming and hawing about the merits of steak over salmon.
So the food usually arrives at some point after ten, except because there's fifteen of you by the time it's come out, yours is lukewarm. And someone's meal always gets forgotten, and arrives half an hour later than the rest so everyone else has finished whilst the poor sod has to continue on. By this point, everyone's shitfaced and by the time the bill comes out no one can remember precisely what they had to drink. Someone suggests just dividing the bill by X which is unfair to Y who only had a salad and glass of water.
This is eventually resolved by the less assertive members of the group paying more than there share, before the subjects of tips come up. By this point, you're the only table in the restaurant left and the waiters are looking decidedly angsty.