User blog comment:B214/Volume 22 spoilers/@comment-201.215.165.7-20170208152747/@comment-26709288-20170215025615

What Rias said at the beginning of DxD is true. Power is everything to a devil. Without power you might as well be nothing. Take Sairaorg for example, born without the Power of Destruction he was cast out by his father and looked down upon by his society despite being born the son of Lord Bael and the only reason he was able to wiggle back in was by becoming strong enough to defeat his brother. Power will always be apart of the class system of devil society. You might look at Issei and think this will destroy the classes of devil society but you should also look at all the other reincarnated devils who didn't or can't make it to Issei's level due to their own weakness or the weakness of their masters, they will still be looked at as nothing but weaklings. Power will always be a form of class in Underworld wether you're a born from a high class or not.