People think 'teacup' dogs have a shorter life span...? *Don't bother reading if you actually believe that*?

In all truth, they don't. Dogs you see quite often, bigger sized, live up to fifteen years or so. I know a vet who had a teacup dog and the dog lived for 22 years, healthy. Teacups really can live up to 25 years or so, so why do people feel the need to stereotype poor, defenseless cute animals?