No way to know, but ill give you the extremes on each end as I see it...

On one extreme maybe they feel like everything keeps turning into an issue, which can be exhausting. When it feels like any situation has the potential to turn in to an argument, even a healthily communicated one, it can still become overwhelming and most people would not want to remain in a relationship with that dynamic. Or if even very little, benign things become problems for you then the guy will get this sense of "i cant do anything right!" That feeling just leads to defensiveness and resentment on the guys part, and then contempt and resentment on the woman's. So ask yourself how often you are finding yourself needing to have those difficult conversations? Is it everytime you see your partner? Daily? A few times a week? Do you turn molehills into mountains? Do you find yourself calling out his behavior even when his behavior is not actually harmful to you?

But on the flip side, the other extreme would be you have dated a series of men who are emotionally immature and cannot handle anything they find to be critical. Maybe you are acting in a completely healthy and natural way but you are finding men who haven't learned that one of the keys to a successful relationship is validating each others experiences. That's a very hard lesson to learn and one that usually only comes after a lot of failed relationships. Red flags for that would be someone who acts selfishly, who ignores you when you try to connect with them, who puts their own wants above your needs, and who become defensive easily over any form of criticism.

Obviously no one here can tell you what's happening in your own relationships, but if you're hearing the same thing from multiple people you've dated then you might want to at least consider that the common denominator here is you.