Excel does not need to be as opinionated or portable as a programming language. This might actually be a lesser of two evils considering what type of user behavior it encourages. (I've heard a similar ethos behind certain design decisions of Go)
I imagine it has to be for their expertise in translating developer intent into practice and refining the shopify specific markup conventions. When I misread the headline as Spotify I couldn't think of why any org, even very front end heavy, would buy them. But continuing to support a language that will always be in it's own lucrative domain makes perfect sense.