The main problem with the subscription model is that it charges the same regardless of user. That means that most casual users will opt out.
For example, I used to purchase a new or updated version of Lightroom every 4-5 years, only when I would add new equipment needing profiles. I don't use or need the latest and greatest features otherwise, and so the total cost vs. usability was good for me.
A professional photographer might be much more interested in the latest features and needs to stay current on equipment profiles. So this person is willing to pay for regular updates. In the purchasing model, the heavier user pays more.
Under the subscription model, the professional is getting a break while I'm being asked to pay more than I'm willing for the software. I made one last purchase to LR6.14 when I added a Sony system. I'll use this software for as long as I can, and if I ever need something newer I will abandon Adobe and look to a new RAW converter.
One other point as to why people don't like the subscription model - I don't keep jpeg files. I keep only RAWs along with the processing metadata in LR. Every once in a while I need an image for something, go back into the catalog and blow off a jpeg for that use. I don't like the idea of my entire file and processing being operated on software I don't own and that I could actually lose access to. At that point I'd have tens of thousands of RAW image files to re-process if I want to use them again. No.......I want to directly own the software.


