The bitcoin blockchain currently meets our needs. Ethereum would be overkill. The way we use the blockchain is very simple. We don't use smart contracts or other things that Ethereum is better at.
Bitcoin has a significant network effect. Because of all the people using bitcoin, there is a big incentive to power the network. Insuring that transactions go through without a central authority. Ethereum is doing great and is very interesting. But it's still less proven and has a public founder. Over time it could become more centralized because of the power of the founder.
However, we're open minded about using Ethereum in the future. Especially when we start using smart contracts.