O_G
"Does anyone get the level of sex they ideally want ?"
Yes, I think that they do, particularly the ones that are note too interested in sex or are happy with the basic maneuvers,so no problem there.
However, for many men, sex is important, essential and they are always looking for something different which is rarely endowed with one women and hence the multiplicity and inevitable boredom of many partners.
spath:
"If you're able to cheat on a wife / partner then you have no respect not only for your commitment but also for the other person"
In my opinion that is not necessarily the case and is far too simplistic an explanation.A man can be "in love" with more than one woman at a time and respect those relationships (at the time).