The FM3 marketing doesn't specifically target gigging musicians, but I think the concept of the FM3 is simple. It offers the same quality of amp modeling, many of the same effects and the same number of stock IRs as their flagship model (ie. Axe-Fx III) at a more affordable price. Some users are primarily interested in the amp modeling and effects of the Axe-Fx III but can't afford it, and this represents a more affordable option.
From the website--- "all in a compact, rugged, all-in-one, floor unit designed for the studio or stage."