Ben, you type so much but say so little.
"Potentiality for the formation of life", water, atmosphere, gravity and heat from the sun? I don't really know too much about abiogenesis, and I also believe we as a whole don't know much about it either. However, evolution is a clear cut undeniable system of facts to how we became what we are today from basic life - which is what evolution is defined as, evolution has nothing to do with non-life becoming life.
Why does there have to be a why?
It seems that you're just after some kind of religious/spiritual answer and you'll happily ignore the science and facts and wait for that to come along.
I agree with what you're saying about doing things for pleasure and non for survival, we've evolved to the point where we don't need to worry too much about surviving, but we still have plenty of residual elements left over from that.
Condoms do exactly what you say, but the urge to have sex isn't really for the pleasure, it's instinctual. To prove this, think about how you feel about the porn your watching before you ejaculate, and how you feel about it afterwards. As soon as you're done, it's straight to the X at the top right. You're essentially tricking your body that you've just taken a step to have offspring, and therefore you body doesn't need to tell you to do this again for a few hours or a day. If you're considering getting rid of the feeling of 'being horny' as a pleasure than I agree with you.
Homosexuality is a means to stop an animal or human in having a child so that they can help raise their nephew or neither. It's important to note that this makes homosexuality natural, normal and decided from birth for all the anti-homosexual people out there.
I've already been over the extreme sports thing in a earlier post.
It's true we have healthcare and food shelters etc, but put back in where we where 15,000 years ago I'm sure we would revert quickly back to what we were, fighting to the death over a dead deer. Look at the guy who sawed his leg off to survive, look at people physically fighting over females, children fighting over sweets, these instincts are still with us. They just lay dormant.
What you said at the very last point could be true. It could be a means of 'showing off' as much as non of us would like to admit it, or to be admired for the act. It could be because it makes you feel good, you maybe can sympathize with the cause. If you got nothing out of it what so ever, you wouldn't do it. The real question is why do you feel sympathy, why does giving make you feel good, it's because it's wired into us from long before we were even humans.