Sometimes, the community is to blame, too. They view this coin as something that is the next big thing while in reality, it isn't, and they're only shilling for their own gain and, just like the developers, when they already profited, they'll just move on to the next 'big thing'.
Indeed. This in my opinion is also a negative consequence of the premine. The business model favoured by premined coins is based often not really on a sustainable usage but on hype and visibility, because the project will have to concentrate the premined funds for a marketing campaign and a paid campaign cannot last forever. Most of those speculating with this kind of coins already for a time should know that pattern, so they are incentived to "play by the rules of the altcoin circus" and hype the coin for a short time, sell it and then jump to the next project.
When you start a non-premined coin incentives are a bit different. It's even often better for the founders if the project at launch isn't known that much, so they can mine/mint without having to invest large sums in hardware. This can lead to a smoother "visibility curve" and also to slower growing prices/market caps, if the team and community do their "job" the right way.
The problem is that most of these projects get lost in the noise of centralized coins. Also, it looks often like these coins are mainly created for the benefit of miners (at least I get this impression in the ANNs of newer non-premine coins) and not to solve a real problem or with the intention to create a real long term viable cryptocurrency. So in these cases they behave actually very similar to premined coins and die after a short hype; even worse, they're at disadvantage in the "altcoin circus" as they have no money created out of thin air for bounties.
The challenge for a really long term successful non-premined coin is to eventually get visibility, and this is not easy. I think the best way to really get successful is to have a kind of USP (for example, some unique function or service) or at least a clear plan what the use case could be, maybe an attached business like an exchange or service provider, and then slowly introducing features which brings the coin closer to that goal. For example I think a non-premined smart contract platform could have that kind of USP, as no popular projects of this kind exists (besides perhaps Signum).