Well, ethereum is simply more stable, thus more reliable when it coems to calculating the desired amount to receive. I see nothing particularly surprising about the situation, good on them for trying competing blockchains, too.
maybe that's one reason why people prefer ETH as you say if in my opinion ETH is an altcoin that up to now has a higher value and price than other altcoins and that's the reason for choosing ETH to invest
If it's about the price, there's another altcoin which have higher value than eth and even more than 3 times higher. This is about altcoin that have awesome reputation and have high volume in the market, so that we know ethereum are more reliable and why people chosing eth than another.