Completely baffling to me, and I've built a huge chunk of my design career using Adobe tools.
Especially then they're not selling the products for several hundred to start, and moved to a subscription model...
From what I've experienced and read, the cost of supporting a platform has to be greater than its sales.
The second issue with this is that many people use Linux to specifically avoid using closed-source software.
No part about Photoshop on Linux makes sense, from any sort of serious business end. They haven't even done an Android tablet port of full-fledged Photoshop, and I haven't really read any plans to support it.
If WINE wasn't a thing, or GIMP wasn't a thing...well, even then; no. This would never happen. XD