One of those reasons is due to fact they can't find a single wallet to hold all their coins/tokens because they invested in multiple shitprojects from misunderstanding the concept, "Don't keep all your eggs in one basket" not knowing it's ever worst when you keep your eggs in multiple unsafe baskets all in the name of investing in multiple source of income when technically they're investing in one (cryptocurrency investment).

Before we start advicing newbie to stop storing their coins on exchange, they have to first be educated on investing wisely.