You're still doing a lot of assuming. Independent SPs are not an agency, they do not have a booker lining up a high volume of new appointments every day. From what I notice based on reviews here, the average terb member sees agency girls for half hour appointments, and some for hour appointments. I have my own incall, I know how many appointments I and a few of my friends have per week. And none of us are having 4 clients a day regularly (maybe once in a blue moon), let alone every day. How can your jaw and vagina handle having sex with 20 people a week? No way. A lot of ladies need time off or get burnt out and only work 1-3 days a week if they do see a high volume of clients because things happen, you get sore, etc.
Now in the $100-$140/hh $200-$220/h price range yes these ladies get a lot more inquiries than we do at the $250-$350/h price range, but again many of them only work a few days a week because they get tired or sore. What you COULD book and what you ACTUALLY book are 2 different things.
Think of how much work it would be for you if you HAD to have sex for 4-5 hours a day 5 days a week, would it be fun at that point, would you be sore or tired? For me it's about sustainability, if I were seeing 20 clients in a week there's no way I could work the next week, even 2 weeks. I don't want to hurt myself or get burnt out. I want everyone to have a good time, and so I schedule my appointments accordingly to ensure that nothing suffers and I don't see "too many" clients.