The brilliant part of it is that it's a double pyramid scheme. The people buying into these ICOs are doing so with Bitcoin or Ethereum that has often appreciated 100x or 1000x from when they bought it. So a company may raise $200M in an ICO, but the investors may've only paid $200K for their Ethereum in the first place. The huge dollar amounts attract more people into the ecosystem, which drives the price of your base cryptocurrencies higher, which means that the prices of these new ICO tokens are even cheaper relative to the dollar amounts paid in the first place, which encourages people to drop exorbitant amounts willy-nilly on ICOs, which attracts even more publicity, and so on.
Until one of two things happens: there are no more buyers for cryptocurrency, the price crashes, and all these ICO investors lose their shirts; or all money enters the cryptocurrency ecosystem, entrepreneurs develop new products & services that can only be bought with their proprietary ICO tokens, Ethereum replaces the dollar as the world reserve currency, and the dollar crashes. I would bet on the former being much more likely than the latter in terms of probabilities, but given that the outcome of the latter is that all savings of people who don't invest in cryptocurrencies are worthless, that fear may be driving a lot of the ICO speculation.
Sure, and they'll hold their value even in this scenario. But (other than the hedge funds) I suspect many people investing in these ICOs aren't big investors in those, and even among those that are, I doubt they'd like to see their checking account become worthless.
Until one of two things happens: there are no more buyers for cryptocurrency, the price crashes, and all these ICO investors lose their shirts; or all money enters the cryptocurrency ecosystem, entrepreneurs develop new products & services that can only be bought with their proprietary ICO tokens, Ethereum replaces the dollar as the world reserve currency, and the dollar crashes. I would bet on the former being much more likely than the latter in terms of probabilities, but given that the outcome of the latter is that all savings of people who don't invest in cryptocurrencies are worthless, that fear may be driving a lot of the ICO speculation.