I actually do like 3v3, having been in a Challenger Team way back than (before the owner kicked everyone and sold it for 350$) and have been ranked in platinum-gold for the past 4? seasons in it, the problem comes with getting diamond or platinum and going vs these 3v3 wintraders because if you just get 1 of their alt in your team you lose, which is a struggle since they're already a strong team who can win games without doing this.
Some of them use the defense of "If I don't wintrade I'll decay because of the low player pool" which is true, but that doesn't excuse EloBoosting and selling of challenger accounts.
I would just link you the Reddit Link but per LoL Reddit rule changes the info was removed for "Naming and shaming".
The 3v3 has a history of abuse from EloBoosting to going back to when there was Team Name and they would sell challenger teams.
I'll try to look for some links but most of the SS were removed, However riot has Perma-Banned the original accounts but the same player just make new ones and do the same thing.
Edit: First MAJOR post about the issue (was well known to the 3v3 community before this) https://www.reddit.com/r/leagueoflegends/comments/3rvj58/high_ranked_3v3_teams_on_tr_wintrade_every_game/
Update to that story: https://www.reddit.com/r/leagueoflegends/comments/3ssft7/today_the_wintrading_tr_3v3_teams_successfully/
Post about NA 3v3 Challenger's Eloboosting:https://www.reddit.com/r/LoLTwistedTreeline/comments/5c7ic5/3v3_challenger_boosters/
Post About the Wintrading down in Challenger 3v3 : https://www.reddit.com/r/LoLTwistedTreeline/comments/9meils/wintrading_in_3v3/
That last one was just 5 months ago mind you, If you look at top Challenger players currently you'll see some with 90% winrate who have quite a few games of them going 22-0 with the enemy team afk, opening lanes etc.
