it's because:
a) founders of ICOs are scammers
b) founders of ICOs don't know anything about what they are doing
c) there are some extra costs and project can't work for long time
d) projcets product is useless and nobody needs it
e) some other random reason
Not really. I known some ICOs that are currently delaying the release of tokens due to the market situation and they're currently focusing in their product which is actually still a good thing.