Why Do Some Women Fuck Easily

Why do some women let guys get between their legs so easily?
Before I got married, some girls and women would only let me touch their tits and no more.
But my wife to be let me fuck her and and spunk her on the second date.
Later our marriage she admitted that she had been fucked a lot before me, most of them were one night stands.
Why did she fuck so quickly when others wouldn’t ?