The day that minimalism got equated with beauty was the day we realized we had too much clutter in our lives, so minimalism = beauty is simply a reactionary concept. Minimalism in of itself could not be considered beauty if you looked at what is considered beautiful art, architecture, clothing, etc, in general.
All of which was pretty heavily influenced by the traditional Japanese aesthetic, which has a pretty strong focus on Minimalism-like attributes.
Minimalism as a positive thing isn't just reactionary. It also serves to bring subtle details into focus, and to emphasize the craft (ie, crafter's experience / quality) as a whole rather than individual details.