There are many reasons the altcoins fail, and they can all be grouped into two categories:
- Altcoiners are wrong about the nature of money.
- The market will only tolerate outsized gains, such as the outsized gains that accrued the ultra-early Bitcoin adopters, once.
In order to profit from a new idea to the same degree as Satoshi, that idea must be as much as an advance over what we have today as Bitcoin was an advance over what came before.
Altcoiners want to achieve Satoshi's gains by creating a new currency while offering merely incremental improvements over his invention (if they offer anything new at all.)