It's been said that God/nature has gone too far to ensure functionality.
We say that especially when it comes to pain, which prevents us from inflicting damage to ourselves.
Pleasure is very nice. Good food is pleasant and also serves as a function for the appetite which is another important function.
Sexual pleasure at some point is paramount and remains entreating throughout life. It's purpose and reasoning is obvious.
People have sex for pleasure all the time. I wouldn't say it's gay, but there are attributes about it that are identical to gay sex in practice, such as wasted semen, which is a really valuable and important material.
Some of us will make it into the golden years, alone. No family, maybe all of our friends are dead, or we don't really communicate with them as much. At some point some of us will look back at the "sex for pleasure" we've had and be wiser about it and recognize it differently.