on guys trying to back out

Of the guys who schedule or agree to a full toilet session, and once it has begun, about what % tries to get out of it or back out? I have definitely read a sentence or two of guys who tried to back out in various anecdotes and comments here, even if it is in a single sentence!

There is the group who requests ft and there is the group who is persuaded or enticed into ft by the domme . . .

Can anyone make an estimate as to the back out attempts or %s?

If you are a domme who has done ft, what excuses or explanations do the guys who are backing out give, if any?

They back out probably because of the taste lol
In all seriousness, it would be interesting to hear a domina's perspective on the subject.