Although pushing io score isnt too fun i get why people do use it cause in my own experience people who are will to get an io of 800+ will be good enough for content that at least im doing ( currently keys up to +9) well others just end up wasting time cause i join groups where leads are accepting based off ilvl.
It ends up in failed key groups cause some players dont understand the basics of play, for example dps groups that never interupt or stand in things, healers who only heal the tank or never cleanse, tanks who dont use defensives properly to mitigate damage and never taunt ranged adds or even hit the ranged.
If you dont want to go to to the website or install the addon in game you can see wat keys youve done and try and get one in all dungs up 7 or 8 and youll get a score that is way more likely to get a 10 key group inv.