Blue Plate Special

Last night I got to have dinner with two of my oldest friends. I say "got to" because we get together roughly every full moon, despite all living within an hour of each other.

Getting together with the girls takes a complex system of emails deciding dates, times, and possible locations. You'd think we were secretaries of the state, but no, just a realtor-nurse-freelancer. Once we had finally whittled down a convenient location and date, the dinner time was emailed to me. She said:

"We decided to meet at 5pm. I'm sorry, I hope that isn't too early for you."

Okay, 5pm is a little early for dinner. 5pm is happy hour, casual meet-up of friends, not really dinner. Nevertheless I didn't really care. I'll get together at 3pm and we can call it supper. Yet again, once comfortably seated in the empty 5pm restaurant, my friend apologized to me (on behalf of both of them) about how early it was. She really hoped it was okay with me.

This confuses me. Why is 5pm early for me, and not for them? 

The only difference as far as I can tell between the three of us is that I am not married and they are. Do they think I'm out partying on weeknights until 4am and I'm just waking up at 5pm? Do they think I need to "see and be seen" and can only venture out at 9pm? Do single people eat really late lunches and therefore can't eat dinner until late?

I ask questions because this one really has me stumped. I don't get it.