Well, for me having good game knowledge and map control is probably more important than just doing damage, damge won't win you a game if it doesn't reach his target, while control over the map can be usefull in more than one way, unless you play "carry supports" who actually are just mid laners who get auto-filled bot for the most part so they pick a full ap champ and pretend to play support, anyway yeah: while supports don't really do the damage, they are the ones who enable the damage to be done most of the times, and since people really can't play the game how it's supposed to be played (so with a brain) supports are the ones who end up having to shoulder the full load of map control, and that also raises your shot-calling abilities since as a support you're usually the one who looks at the map the most. So yeah, while you mostly won't get those big, flashy pentakills, you will probably be a huge factor in making them possible, unless you actually got carried, everyone can have some bad games or maybe just get carried because someone in his team is just so much better than the enemy team that he solo carries a game leaving you with nothing to do (seriously, I'm happy when it happens, but it feels awful to not have anything to do on the map, especially when you can't even farm...).
And yeah, trust me, after playing support for so long (I think I started at the end of season 3 or even before that) I can assure you that, at least up to plat (I've seen a lot of plat games from my cousin, and even there other than the support, people don't even know what map awareness is...) no one other than the supp tends to have any knowledge or awareness of the map, laners focus too much on theyr lanes...