I kinda think it's because a they're a freelance type of worker and the ball is always in their court, because a lot of people want a lot of things done from them. They can pick and choose which jobs to prioritize, and which ones to just toss aside, they have no written agreement that they owe you anything until they actually show up and start doing work. Even then unless you get in writing, they still don't owe you anything.
Your house might be a small job for them, or a hard job, or just something they don't want to get into. Maybe they have a much sweeter gig elsewhere right now.
