I don't get it.
They make little sense from an economic perspective. Big dog = more food costs, more mess. Plus, anytime you have an animal over 50 lbs, you run the risk of that dumb fucker jumping into your lap and rupturing a testicle.
But there are people that wear a ton of jewelry, have huge tires on their vehicles or wear unflattering clothing with garish colors. We all overcompensate in our own ways.