Why do people assume that they're after the age if there's a big age gap in a relationship?

It can be anything else. He likes her or she likes him for their personality, common interests or whatever but why is the age of ways the conclusion? For example i can say, i can fall in love with a 15 year old girl if her personality and interests matches my criteria. it's not because of the age but of course i find other teens cringe. Also i can fall in love with someone who is older than me and about my age.
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+1 y
I just it's time that anyone realized something that's why nobody is answering it
Why do people assume that they're after the age if there's a big age gap in a relationship?
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