It seems that every altcoin has its difficulties to scaling up, mostly the solution is POS.But it is hard to control the speed of the inflation in POS, so lastly a new altcoin will come to the market for alleviating the problem. It is just a vicious cycle....
It also allows for innovation - as most new coins offer an alternative which can be tested on a small scale (such as segwit for litecoin) or as an alternative in its own right. Or increasingly as something that can be pinned to and interwoven with bitcoin.