Hooking up: Nice, some fuckmeat, all done ok bye fuckmeat, yes yes I know I was amazing, now bye and I don't care about your inevitable suffering in this life.

Being in a REAL relationship: My soul is bonded to yours we are one body and I am constantly worrying about you and I won't tolerate anyone disrespecting you

And that's why I can't be poly. 99% of sex is disrespectful, so no way I want other people doing that to my partner. Only WE can disrespect eachother like that.