Either the munters are delusional and barely get any business or many men are so desperate they will fuck anything.
I was stuck on an overcrowded train that had stopped between stations while Network Rail removed the herd of wildebeest that was blocking the track, or something like that. I was lucky enough to have grabbed a seat before the carriage became totally rammed, but not so lucky as to be sitting next to anyone pretty: next to me was a fat, ugly, middle-aged woman with lank hair, bad teeth, blotchy skin, etc. etc.. Said swamp-donkey spent the whole of the twenty-minute delay braying into her 'phone. She didn't seem to mind, or even to notice, that I spent the same period staring down her ill-fitting blouse, which was deeply gapped open to expose her sagging, freckly, veined and slightly hairy cleavage.
For days afterwards, I couldn't get that image out of my head. Eventually, I looked for a fat, ugly, middle-aged WG to wear a cheap, badly-fitting business suit, sit next to me, and wank me off while we otherwise ignored each other. Since that description applies to an awful lot of WGs and indeed punts, I found what I wanted very easily indeed.
Oops.
NIK, I was going to use this as an example of a possible third reason why punters might book munters, i.e. highly personal wish-fulfilment. But now that I come to re-read it, I see that it's more a confirmation of your assertion: at the time, and in a very specific way, yes, I was desperate.
Still one of my all-time favourite punts, though.