The natural end of sex is procreation. Interfering with that natural end is imposing our desires on a natural process and also holding ourselves back entirely from our spouse.
For practical reasons, look at how the divorce rate has exploded since the rise of oral contraceptives. Look also at the rate of children born to unwed parents. It's a very sad state of affairs currently.
Not really. Humans usually have sex for bonding purposes only, and it has always been that way. Humans used to only have 2 to 4 kids over the course of their lifetime, spaced 4 to 7 years apart, when they were living under natural conditions. Humans take decades of very attentive care to raise, and it's to everyone's benefit to have relatively few of them and not to have multiple infants and toddlers simultaneously so they can do this properly. It's also better for the sustainability of the tribe not to out-breed your resources.
The only reason that changed is because agricultural lifestyles alter the body fat composition of women. Our lifestyles used to keep us lean, which meant women weren't fertile very often. Agriculturalists eat fattier foods and the type of exercise they get doesn't reduce fat as much (even if they are in very good shape), which means women are fertile almost constantly. That's profoundly unnatural for humans, and also unhealthy.
Birth control has done nothing but restore the natural rhythm of human reproduction.
The divorce rate is only the official record. Couples were separating at high rates long before legal divorce became less taboo. Also, a lot more women were simply dying at young ages due to reproducing more times than their bodies were built to handle.
The divorce rate is the highest for the generation that married right before divorce became acceptable. They got divorced in a huge wave after their kids left for college. Couples since then divorce at much lower rates. In fact, for couples who married in the last 2 or 3 decades while in their mid-late 20's, the divorce rate is only 20%.
Couples who reproduce younger also divorce more often, and the early childraising years are the least happy years of marriages.
The biggest predictors of successful marriage are both partners being educated, marrying for the first time relatively late (25 to 30), and having well-spaced children (and relatively few of them, consequently).