Only then, when the deadline for fulfillment of obligations on roadmap comes, projects do not fulfill them, and investors, seeing that the road map is not fulfilled, sell tokens.
Then it is even mostly too late to sell because there are no buyers. If there are no updates and you lose trust, how should someone else gain trust and buy?
sometimes, this happens, that you can still sell tokens to someone. it may be in different. in many cases it is possible to return the lost, but not always. but I'm sorry, that everything will be fine with it
But it doesn't feel morally correct if you sell something to someone that you know will destroy the investment of another person.