It's really hard to place systems to counter, warn or (if) ban smurf accounts because it's a near impossibility to spot one at its creation until the account is doing oddly well in a match for being lvl 1. You can't accuse all low level accounts for doing extremely well because that's blunt and would create a lot complaints. If you assume that one computer is the source of multiple accounts, therefore it the others must be smurfs, then the same applies.
I often see Twitch streamers use smurf accounts to do the "Challenger Challenge" where if they are a challenger in their main, they will make a smurf, and play ranked, get to Challenger as fast as they can. Diamonds and Platinums and Master Tiers do it as well but less commonly. It does add an aspect of replay value for old/seasoned players who are getting really bored of playing the same game and match scenario.
I suppose that I don't want smurf accounts to even exist for the sake of the Bronze and Silver players climbing. If it becomes far too common and is rampant in my region then I would begin to send support tickets and complain.
I play mostly normals so I hardly get smurfers, but it still matters.