Human Selective Breeding:Any Benefit To Cultural Selective Breeding?

Was just wondering sitting around tonight if there was any physiological benefit or edge in humans selectively breeding. The reasoning is clear in political forums as seen in Royalty throughout the global Monarchies, the passing of 'power' such as it were. We also see the benefits in the selective breeding of animals, whether it be domestic food sources (also seen in horticulture, many Marijuana enthusiasts would agree), pet, or to to fix genetic congenital issues within a breed or stock.

But what of the benefit in the physiological make-up of people in general? The DNA essence? Some would argue that the breeding within a small line of genealogically similar people will promote negative genetic disorders while others will contend that we in fact originated from 2 people (as recent genetic testing has proven) so the 'bad' genetics are 'bred out' and therefore ultimately produce 'superior' offspring (the royal lines)......im genuinely curious for some information and opinion on this..as well as some insight as to why it is still practiced in many cultures even today, even in exceptionally rich (old old money) places of political power (see the 6 degrees of family seperation on just about every president the USA has ever had)...any thoughts?

The main problem with selective/restricted breeding is who exactly decides? The government? It would probably be to satisfy their own selfish agenda ultimately. Also is there any real way to completely eliminate "bad" genes? Even if we did get rid of all/most of our bad physical qualities through selective breeding, couldn't new ones show up? No matter what we do we'll never be perfect. Those are just my thoughts .