I work for a not for profit, and it's fairly standard to expect people to share when possible. At the meeting I'm going to next week for example, they priced the rooms for 1, 2, 3 or 4 people.
I hardly every go that route, I'll combine it with a mattress run, and I can't get a room for what the per person combined rate is I'll cover the extra cost. It's more then worth it for me. It's not a written policy, it's just what some chapters do to keep the cost down.