For me most likely a practical element: working with exact appointments all day every day. Always having to be present for each client when I am required to, in ways they want me. I've worked highly flexible and autonomous times in my whole career and like it this way (I think by default, why I choose to work this way), so this aspect would be hard to get used to. Also, I would probably struggle if I had too many clients, probably would not see more than 2-3 per day, I am too much an introvert for more. But I actually think that working as a therapist part time might be interesting for me.