I typed out "and boys do too. Heck, everyone likes gifts." then deleted it.
Gifts are good when they're accurate. Accuracy requires understanding. Thus a gift is a display of your closeness to the person.
But unfortunately a whole lotta gifts require mon-ay, and a whole lotta people's stuff they want is stuff they can't afford, otherwise they'd have it already. I'm not saying girls are shallow, nor am I saying that all girls will leave you if you never spend money on them. There are other ways to get happiness -- but the basic point Mad Monkey made, that girls like money being spent on them, is fair enough.
And personally, I'm fairly content without money - but money buys comfort!