Most Helpful Guy
That's just some trying to be nice about it. Sometimes it's the truth, they have issues to deal with/ too much on their plate without a relationship to also deal with. Other times they've simply met someone else they like better (if for no other reason she's someone new he hasn't seen naked yet) and are nice enough to dump you rather than cheat on you (actually kinda rare, most will juggle you both until he tires of it or is caught). For the rest it's an outright white lie: it's really one or more things about you that are deal breakers for him.