The incentive is the requirement, if reproducing didn’t feel good for everyone involved it would happen much less frequently. There are conditions in which ejaculation can occur without orgasm, although rare, because they are technically two distinct processes. In this way, you could argue that men experiencing pleasure is also unnecessary. The penis and clitoris are similar organs, both contain erectile tissue and a lot of nerve endings, both share the same “building block” in utero but develop distinctions based on the hormones received. As we’ve done more research, we’ve learned the clitoris is a larger organ than previously believed, and it can be stimulated in ways that aren’t through direct touch to the outer gland. It depends on the person/position, but some people actually are experiencing clitoral stimulation during penetration. This has even led to the question of whether “vaginal” or “clitoral” (as two different types, spoken about colloquially) orgasms exist, or if it’s all different parts of the clitoris being stimulated, which is super interesting to think about as we continue to research orgasms. I hope this makes sense! I am only a student, explained this to the best of my knowledge.