I believe there are a variety of reasons people make or buy other accounts. The main reason most likely is to play people at a lower level to beat them more easily. If you look in challenger, a large number of players have 2-3 accounts in challenger. I am low elo, but I believe a lot of them do it for the grind, and to find matches easier. Other reasons as well I am sure.
You see people bitching about smurfs all of the time and I have never seen a good answer given. I know this would not fix everything, but in some ways it could address some issues. For pros, I am unsure how they get smurfs (i.e level accounts themselves or some other "punishable" way), but this would help them achieve a new account faster and potentially save them money in re-buying champions they own on other accounts. The price would probably have to be more than $60, no idea how to determine how much Riot makes off of smurf accounts in boosts, champs, etc.
Right now low leveling sucks because half the players in each game are smurfs ranging from bronze - master. Although this would still exist, it may stop a few people from doing it who are willing to spend the money. And since your accounts would be linked, it would lower some smurfing toxicity as players would not want the linked account to be banned.
I will admit it probably does not make much sense, just throwing some form of an idea out there.
I have a second account I originally used to mess around in bronze since I suck. Now that the account is a similar elo to my main, I use it to play with some lower elo friends or try out some different champions or comps. I also tend to care a little less when playing on that account about losing, which yes may be bad but I have found to win more games since I am not as butt hurt from losses and generally have more fun win or lose.
