That doesn't make any sense - why would it be that you get three times the amount of ranked points on 5v5 than you do on 3v3? Twisted treeline ranked matches are not three times easier, or three times shorter, so why do we get so much less for their wins?
As an avid 3s player, I feel you. I feel that 3s is under-rated, and it is only a few tweaks away from being truly competitive.
The reason why it doesn't get as much reward is because Riot wants to emphasize that 5s is the "real" game mode. The true essence of league of legends. The truth is... 5s is the real League of Legends. 3s is just a little fun side thing that happened to become competitive enough to warrant its own ranked queue. While it seems like it may be ignored, It is much more respected than ARAM and Dominion. The fact that you can get ranked rewards at all through 3s is actually pretty damn cool.
I don't think it has anything really to do with the maps themselves, simply the duration of the games, and since 3v3s has a generally lower game time, Riot saw fit to lower points gained.
I think its because the game is "balanced" around 5s. I'm not trying to justify it, but as the game is balanced(or at least supposed to be) around 5s, there are things that you can technically do in 3s that is "OP". At least that's what I ran into when i tried 3s last year for rewards. Playing tanky champions was really the only way to go and as that wasn't my think, I was REALLY turned off to it. Many champions, especially supports, just can't compete as they aren't viable there. Also as 5s is what RIOT pays attention to, I'm assuming that it is what gets the most attention. You are rewarded more because there's more to do and it requires more teamwork (more people and such and time investment).
The rewards for ranked teams were based on the fact that getting a team going takes more effort than jumping into solo queue. By that logic, it is more effort to get five people working together than three, hence the difference in points awarded. On that note, I don't think it should be a 1-3 ratio, but not much you can do about it.
