I think there is more to that, like last minute cancellation, make a booking and not show up, wasting time, etc.
Are your number, name, description logged in ugly mugs or their group chat for whatever reason possible.
They prefer certainty, if you booked for 11 o'clock and have a record of either late, last minute cancellation, or no show and their regulars who always come on time making a 10:30 booking of course their regular will get preference.
Is the same like any other business.
When i am still active visiting AMP, Lola use to pull the girl out in the middle of the session with another customer if i want to see her, in my defense i didn't know this been happening for a while until the reception told me when i ask her she said you are VIP lol... I am impressed but told her never do that again is not fair.