Robot sex

I was just looking for ff of Optimus Prime x Megatron after watching the recent transformers movie up until I saw there's smut. I'm so confused about robot sex like them terms and why do they need sex organs to begin with? they could just build a baby(literally) even though there was a thread that that could get pregnant. Idek what to think like maybe they could kiss and hold hands and smth like that but I forgot how imaginative people can be lmao I need to watch the series