You get some benefits with higher levels, that's true... but even if you are higher level you need to wager even more to be eligible for some good prizes! So who wishes to gamble as a high roller can start from the beginning and with a few sessions you can get that higher level and all the prizes for leveling up. With just buying a higher level you miss all that!
Missing all those benefits of leveling up is not the main problem, the main problem may come when it is against the terms. Most casinos does not allow selling accounts, the risk will be on the buyer side because buyer need to spend some money to get the account but the account might be suspended immediately once the casino notice that the account changes hand. I would not recommend anyone to do selling/buying gambling accounts, it does not worth at all.