Thanks for all your answers :)
It's a bit difficult to come up with good examples.. I do not mean a FWB type situation, but a relationship situation.
Being with a truck-driver could be an example.. You know upfront, but you cannot really fathom what it means in day to day life.

Another one concerning a hobby: Yonks ago I was with a bloke who always listened to a police scanner. He really loved that and whenever there was something going on, like a fire, he'd drive over there no matter what. He was absolutely nuts about me, but as soon as he heard something interesting on the scanner, it became his entire universe, whether I was waiting for him or not, had dinner ready etc.

If I had tried to do something about it, I would've tried to change him. Is that the right thing to do? I knew upfront he was seriously into that, and sometimes it was fun. But I couldn't guestimate its influence on me or our relationship.
In the end it became terribly annoying.

And I know it's easy to say: if he loves me, and I him, we're cooking! But what if you're mostly cooking on your own, lol.

Even if you knew going in that he was addicted to the police scanner and you (and he) went in anyway and without discussing it, if he was consistently letting meals that you prepared get cold in favor of ambulance chasing, I'm sorry, but he was not absolutely crazy about you, he was taking you for granted...

PS: Expressing dissatisfaction about something that is going on in a relationship is not trying to change someone, it's trying to save or improve the relationship...Think balance...