Better air consumption... is it because 'high' person do anything 'slow'?
Maybe it's not really an advantage at all for those who choose to do so and think that it gives them that advantage.
Imo, it also cloud the judgement to react to certain situation or emergency etc. The habit gives the idea that it makes diving more enjoyable and they stick to that, which sounds like an addiction and addict's point of view, very subjective.
And why people here react hard to this, I think because diving is the sport that involves the safety of others too. We are not created to live in water, we need life support equipment etc, it's not a natural activity, that's why it involves many risks.
I must say divers are very social to other divers, many of divers don't hesitate to help others in danger or in risk, regardless who you are and which group you are etc.
So the activity involves a lot of party, DM, buddy, divers around you, rescue etc and imho, it's just right to do it in responsible way and shouldn't risk your life and some other's for 'unnecessary pleasure'.
My 0.02 bar.