Why do ICO choose Ethereum?
because it is the most hyped platform and because of that there are services like myetherwallet for example that made it easy for people to have an ethereum web wallet despite having a real desktop wallet being near impossible because of the bloated blockchain. and that makes it easier for anyone to join these ICOs.
is there an alternative to Ethereum ICOs could use?
there are lots of them!
- Waves,
- LSK,
- NEO,
- ARK,
- Ardor,
- Bitshares,
- Counterparty (XCP),
- Ethereum Classic (ETC),
- Expanse (EXP),
- NEM,
- NXT (NXT),
- Stratis (STRAT),
- Tezos
and finally Rootstock (RSK) which works on top of bitcoin
Yeah, there are many platforms for ICO conducting, but ethereum is still the most popular and convenient for developers IMO. Recently buterin made some kind of statement where he said about burning of ETH tokens via increasing fees for ERC20 projects. It can be very harmful for ethereum so others platforms would be much more attractive. Only time will show.