-They waste time of actually leveling up on your main account
-You want to buy more Rp for that account for skins..
-You proberly will go on your main less= less leveling up=don't improve=don't improve no higher rank and i bet bots don't help...
There are alot of reasons why people would take an interest in leveling a smurf. To some people, leveling up a smurfing ISN'T a waste of time because they enjoy it and they have access to another account. Some people could be coming back from a 6-month hiatus so they might make a smurf to ease back into league. Some people make smurfs because they care more about being able to play ranked on a fresh account. And theres more reasons as to why people would have a smurf account.
Don't assume everyone cares about skins. Thats not always the case, especially if the person can't afford it or simply doesn't want to purchase them.
All new smurf accounts start at 1200 elo (average) for ranked. I feel like smurfs work both ways in terms of how effective they can be for each player's individual skill. For example, if your main was gold 3 , playing ranked on your smurf will prove whether you're capable of getting to the elo that your main is at, displaying a test of your skill. Conversely, if your main was bronze 3 , playing ranked on your smurf lets you play at a higher elo and should help you understand crucial skills you may need to get to this elo and you might improve in the process.
-If you go on PVP and kill someone alot they might rage and not play again..Not cool..
If a person is going to rage and quit a game after having a bad match, they're probably weren't suited to play this game in the first place. Besides, there are alot of other reasons that make up for majority of league players leaving (like toxicity in the league community or disliking changes to the game).