In British royalty, why is it that if a man marries a princess he doesn't become a prince?

If i could only marry the beautiful Princess Anne, i wouldn't need any fancy title or name, just being married to that gorgeous looking lady would be more than enough for me.

Sexism. They are one person, and that person is the husband.

Being a Royal Princess who marries a non royal, doesn't mean the man takes her title. Much as a woman would take her husband's title, if any. The title carries the status which can't be passed onto a male 'commoner' spouse.

Sexist.

Because females take their husbands titles.

Just tradition - and it really doesn't matter. They're just titles, labels. Who cares?

That's how it works. The woman takes the man's name (and/or title) when she marries, but, it doesn't work the other way round. Or, at least, it didn't in the past.

You may as well ask why Miss Jones becomes Mrs Smith when she marries Mr Smith.

Sir Prince Philip did.