User blog comment:TheTobarMethod/A Reason To Not Whine About Low Elo/@comment-6435632-20130729195128/@comment-6435632-20130729224812

Supports are more capable of carrying games than ADCs are. If you have a bad support, your ADC is basically laning alone. If you have a great support, they can babysit the ADC like a boss and get them fed even if they're not so good. I've carried bad supports before. I don't main support but I do play it and when I do I support pretty dang well.

Although it should be said that if you insist on only playing one role, you're going to have problems. Sometimes other people take that role. You'll never be able to guarantee the same role every game, and being unable to fill needed roles is a problem.