In the semiconductor industry this role is called Field Application Engineer. They do serious work, not just slideware, as your chip probably ships with drivers that were designed months or years before you could get significant time from the customers engineers (which generally only happens after you manufacture, but you need software to prove it works well before that). So these guys are the ones who adapt it, and their feedback is valuable as they are the ones who build understanding of the customer.

However, at my old employer they didn't get commit rights to the main software repos. They had to carry around a bunch of patches which were gradually cleaned up and integrated. As I didn't directly work with them, I don't know if this says more about them or the guys managing the internal development.

It's a role that fits a different personality to that typical among software engineers. If you're bored as a dev it may suit. Pointless to try to shoehorn people into the role that don't suit it though.