Many ICO launch payment gateway choice ETH. any other crypto coins why not use in ico payment gateway.
ICO were done countless time in cryptocurrency world using ETH as their main network at first, and own network later.
But now ICO facing downtrend because many scam projects steal investor's money in much amount.
Although there are some ICO's launch with other coin than ETH, the usage of ETH is the most popular in ICO.
Many ICOs using ETH maybe because its more popular than others. Its true that first time they launch ICOs using Ethereum network but after a few months they change to their own network. Like Wanchain, first ERC-20 and before launch in exchanger, they making swap for their investor to their own blockchain