Yes. You are completely missing something.
Long story short, virtually EVERY bet on the roulette wheel has exactly the same house advantage, and therefore is just as good/bad as any other bet. (The sole exception to this is a little-known bet called the "Breadbasket" bet on the 5 numbers, "0, 00, 1, 2, 3". This bet is a bit WORSE than all the other bets.)
OK, so what are you missing? Think about it. You bet $2 on every number in the 3rd column. "3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36". That's $24 bet.
#12 wins! What do you get back? Well you WIN $70, but don't forget you also get to keep that $2 winning bet that is sitting on #12! So you have $72 total.
Now let's figure it out the other way. Instead, you decide to just put the whole $24 on the 3rd column. Those are the same numbers.
#12 wins! What do you get back? Well you WIN just 2 to 1 on your money. That's "only" a $48 win, but don't forget that you also get to keep your $24! $48 + $24 = guess what? $72! It's the same!
OK, let's do just 1 more example. This is the one you mentioned.
$6 bet on the "One Street", (that's the 1, 2, & 3). It pays you 11 to 1. YES, that is $66, but don't forget that you also get to keep your 6-dollar bet! That means you get $66 + $6 = $72!
That's the SAME THING as if you had bet $2 on "1", $2 on "2", and $2 on "3". If you bet $2 on each number and #3 won, you'd "win" $70, PLUS you'd keep your 2-dollar bet. That's $72 total!
Finishing up - As I mentioned before, ALL bets on the roulette wheel have exactly the same house edge. (Excluding that weird "Breadbasket" bet.) You can mix them and match them and change them around. When it comes to the end of the day it makes absolutely no difference. Nobody has EVER found a way to beat roulette, and nobody EVER will! YOU will not be the first person in history to figure out a way to beat it either. If you like roulette, HAVE FUN with it! It IS a fun game! Just don't ever expect to be able to "beat" the game!
Try to BEAT roulette at your peril.