Why are there more MIL than FIL problems?

Even when a FIL isn't your biggest fan, he rarely plots schemes, gossips nonstoppable to others or plays mindgames. The father tends to more straight-forward; then once he knows you guys are happy that's it. There is no elaboration.

Unlike the crazy MIL stories; even if you're happy she'll continue remembering the one trait she didn't like in me (not letting go), play games, tarnish your reputation and not stop unless your spouse intervenes. I've heard even some guys have problems with the MIL too.

Whenever I heard miracles stories about the spouse parents accepting you, it's the FIL that warms up but the MIL doesn't; she just pretends to be nice while forever disliking you. Serious why? Why are there more issues with MILS than FILS?
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Correction: This question isn't about me. It's in general. I've been noticing this over the years too much. The FIL have a higher chance of coming around (they just need confirmation that you guys are happy and that's it; end of story) but if a MIL dislikes you so badly then OMG there is literally nothing you can do.
Why are there more MIL than FIL problems?
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