Quote from: bountyjunkie on January 10, 2018, 08:05:49 PM

What are the merits and demerits of only accepting ETH as vs say ETH and BTC or other coins like BCH, LTC, DASH etc.

Well, the easiest way to reward your participants is sending back the corresponding amount of tokens to the Ethereum address that sent ETH to the ICO address.

As most ICOs use tokens that are ERC-20 compatible and built on the Ethereum Blockchain, it's not hard to figure that they'd send the tokens to ETH addresses.
The ICO creators probably want to collect the money as easily as possible, which would just be sending back the tokens to the address from which the ETH originated, which is quite easy to do.

So they're probably just sticking to ETH to make it as easy as possible for themselves to collect all the money.