I can answer this, having been in the business of selling D&D books since 1993. I didn't see the 1e-2e changeover, but I saw the 2e black books, the 3e books, the 3.5 books, the 4e books, the 4e Essentials books, and the 5e books, and now this. Is that enough to weigh in?
I mean, ultimately it IS marketing - but the difference is SMART marketing VS FOOLISH marketing. The big difference as I see it is: EVERY SINGLE previously published book was made obsolete by those "Edition Changes" and went out-of-print until a "compatible" replacement was made, or if it was never made, the book was just discarded. Worthless (until collectors came in many years later). When 3e came out, our 2e books were garbage. Blowout stock. When 3e came out, our 3.0 books were garbage, blowout. When 4e came out, our 3.5 books were garbage, blowout (until the 4e backlash that made them HIGHLY SOUGHT out-of-print collectibles selling on Ebay for BIG BUCKS!). 4E essentials did not harm 4e, because it was compatible (their first attempt at doing so) AND YET, the community wanted to call it "Four-Point-Five" (familiar?). When 5e came out, our 4e books were garbage. Blowout.
Now there are ~20 (I'd have to count them) 5e products IN PRINT that WotC DOES NOT WANT to ruin their chances of selling MORE of. They're happy to let the 3x 2014 core books go OOP for their new books. Replacements they ARE - that's why they have the same name! BUT - they don't want you to think that the other books are not compatible with them! They want you to be able to buy them! AND if you don't buy their new core (for example, because you don't want to buy new Core books, or you're happy with your 5e 2014 books, they want you to buy THE NEXT ADVENTURE in 2025, or whatever they have going forward after the core are out.
It's as simple as that.