Wow, I didn’t know antique maps were a hot collectibles, or that full atlases were being broken down like that. I guess a lot of collectors might only be interested in their own state or even city/town, hence the disassembly. But the historical growth of the country and states being established from the colonial period all the way up to the 1950s makes for a lot of history to explore.
I’ve been into newspaper comic strips lately, which has some similarities to historical map collecting. I don’t try to go any further back than the 70s, but a lot of serious collectors go back to the 1940s, 1930s or even earlier. Unlike what you’re experiencing, collectors don’t seem to frown on separating sections into clipped strips, building runs of a particular title, etc. rather, most of the criticism seems to be directed at what the newspapers did to cram more strips into a given page space - shrinking the overall size, trimming the panels or removing some altogether, stuff I never knew went on. For example, the Sunday paper of my childhood had a full-page Dick Tracy on the front page, but I’ve read that papers that ran those same Sunday strips in half-page format did so not just by scaling down the size and re-formatting the layout, say from a portrait to landscape configuration, but also by removing a few panels altogether! It’s like taking out part of the story that the writer/illustrator created! So a purist collector of truly complete strips really has their work cut out for them. Maybe it’s better to stick with collecting weekday strips, which I don’t think went through any of these shenanigans.