wtf?

so i saw a viagra commercial recently and it said "if erection lasts for more than 4 hours, call a doctor". wtf? why would i call my doctor with that? i dont know about you, but id call my girlfriend, my friend's girlfriends, id just call someone who isn't a man or a doctor. also, i dont really understand viagra or levitra. from my perspective, its pointless, as a 21 year old , i need some type of pill to keep it down, so in the end, viagra...wtf?