Because if you're fed up to the point where you'd give an ultimatum, then the only purpose the ultimatum serves is to make them go through the motions for your own benefit. If I'd have said "Your games and friends or me", he might've obliged. But unwillingly. Then there would be resentment. Then there'd be a whole new set of problems in place of the old ones. Instead, I talked and TRIED to initiate compromise, and let him see what he'd come to on his own. His own inability to cut back on them told me what I needed to know - that I wasn't really worth it for him. And if that's true? Buh-bye.
She could probably give in to this guy's ultimatum to keep from losing him, but she won't feel right about it. She'd probably feel the same kind of resentment. The relationship would probably end up fracturing anyway. But it'll have done so with Claire having made her first time with someone who, quite frankly, is a dick. Ultimatums never amount to anything good when they're accepted. One should never accept an ultimatum, nor should anyone GIVE one to a person they claim to love.
Ultimatums are never the way to get what you want. The way is compromise, or even willing sacrifice.
Claire, did you compromise with the guy? Did you do other things besides full-out intercourse? I know it's not exactly the same, but I REALLY couldn't sympathise with a guy giving sex ultimatums if he's getting head, or at least handjobs.