Responses
Because semes are usually portrayed as these good looking popular dudes who aren't very expressive. So when that facade slips up, it's extremely gratifying, especially since the ukes in these manga usually are the complete opposite ie they're sweet/innocent/naive/clumsy/sometimes pathetic. Read some puppy semes/power bottoms and most likely you'll feel the other way.
I think its because you want to be possessed by a person who wants you to think only of them and you don't express your jealousy openly. Just a hunch tho coz I'm the same
Why is it.. THAT I CRINGE AND GET SECOND HAND EMBARRASSMENT WHEN UKES GET JEALOUS?! BUT WHEN IT COMES TO SEMES I SCREAM IN HAPPINESS?!!!