Guys with no stamina are useless to her.

Ok,
so..
i have this friend (i know likely story) and if the guy can't keep up with her.. there useless to her.. lol
she can have sex probably 30 times a day if she could, but the guys can never keep up.
and see... we think that if guys cant keep up.. what's their purpose.?
so im wondering if its normal to think that guys are useless if they cant entertain us,