I've noticed this too. I usually like to start with an hour for the first time. Two hours can seem like a long time and often a lot of money if you dont click. Been there. Done that. I've also wondered if they want a 2 hour minimum so they can spend time talking. I had that happen once. We spend the first 15 minutes at least going over my kinks and stuff. I don't like a lot of chit chat before a session so I'm leery of mandatory session lengths.