It's pretty simple. Besides the typical ICO scams that everyone knows exist, with investing and business in general— a lot of startups fail. And when I say a lot, I mean A LOT. And taking note that cryptocurrencies are still pretty new conceptually? Multitudes more are going to fail compared to the typical business/startup. Cryptocurrencies at it's current state is going to be hit or miss. A lot of projects are going to be created, and a lot are going to lose relevancy.
Exactly this! I read that 90%+ of startups fail, no matter the type, so that's just in their nature, to fail. That percentage is of course much higher when it comes to crypto startups as huge majority of those don't really have any reason to use cryptocurrencies, but buzzwords like "decentralized and "blockchain" are what attracts investors and speculators.Why do so many ICOs loose in value when they are listed and what are the lessons to learn from them to gain value overtime?
There are two main reason why their price goes down a lot: first is because their utility token doesn't really have any use case at the time of the listing (and usually not even after few years lol), and if there is no use case, people will just dump it. 2nd and equally important is bad tokenomics, where they sell way too much in early sale phases without locking/vesting so those early investors who paid a fraction of the announced "ICO price" simply dump the tokens upon exchange listing. 
