Why do you think good altcoins fail to keep going? It seems there are some that are good and people collectively have put in tens of thousands of hours supporting, but the team decides to give up midway.
I think its because of the unstable value of bitcoin,they aren't go with the changing value, even though they coin want to be discovered and be popular in the world of cryptocurrency still they are can't go with the flow, so many coins have been fails to arise and many coin devs left there coins because of lack of interest and even because the insufficient fund to keep their coins alive.