Why do guys say it’s “not you it’s me” when ending things?

The guy I was seeing ended things with me today.. When I asked why he said it’s him not me, and that I’m a good person basically (not exactly what he said but) and that he just needs to focus on him and get his life together… This is the second guy to have said something like that to me… it’s always “I’m wife material but not for them” … but that just makes it feel like it’s me at this point or not good enough… because why waste my time saying they want to be with me but then all of a sudden say that stuff… I don't know..
Why do guys say it’s “not you it’s me” when ending things?
Post Opinion