Because stats don't tell the full picture do they. Stats tell part of it but the best way of judging a player is by their contribution and what each fan sees from a particular player.
What I see from him is an excellent shot stopper, who is one of the best in the league in that regard, great at saving penalties and is fairly young. The negatives to him are that he is too over confident with his kicking and is prone to mistakes. But find me a goalkeeper around that isn't prone to mistakes. And those keepers who do make them less often, wouldn't even entertain the idea of playing for a post 1987 Everton FC.
The stats about how many he conceded include his time for Sunderland, a team that was the laughing stock of the league and went on to suffer a double relegation. I wonder how David de Gea's stats would look if he played for that side?
Some of the stats we've looked at are premier League (including a small portion for Sunderland compared to that of his time with us) and some with only Everton appearances. Neither make for a good reading as we've noted.
In his time at Everton or something he's conceded over 100 golazos.
In regards to the rest, stats can absolutely skew things, but I have watched him with my own eyes and I don't think he's particularly good. He's terrible with crosses. He almost always blames somebody else. His distribution is borderline woeful for a number of reasons.
He is good at saving penalties though.
I almost always praise him in here for doing things well, but more often than not I find myself lambasting him for the crap he does poorly.
The thing is as well, United fans don't even think they've got a good defence. They have De Gea. A goalkeeper who stops almost everything thrown (lol kicked) his way.