Not everyone needs 'full Photoshop'. Not every 'professional' is a professional photoshop artist. Far fewer people need full Photoshop than use full Photoshop. Lots of Photoshop conscripts are desperate for alternatives. I've been using Photoshop for over a decade, and any chance I get to use something else, (Mari on desktop, Procreate/Sketchbook on iPad) I take it. Either for better features, or more streamlined workflows. Photoshop isn't the be-and end-all, its just the lowest common denominator, and/or the best at heavy photo manipulation. Plenty of apps are actually better at sketching, or painting, or photo processing, or other work. And of course, Photoshop is rental only.
I agree about 'not everyone needs full photoshop'. About a year ago, I was part of a market research group for Adobe. At the time, I had the first versions of the Adobe Touch Apps that were slimmed down versions of their desktop apps. They asked me what I thought of their apps and I told them that although they were fun to play with, they have no relation to the desktop software. In other words, it didn't fit my workflow and that there were no benefits. So, they came up with their new apps. The Adobe touch apps that you see today are a result from this research. I had suggested (and I'm sure a few other professional graphic designers like myself suggested) that they make these apps as a slimmed down version of the primary desktop apps BUT that they would be part of the creative workflow process. For example, if you use Adobe Fix, after you make your adjustments and edits, you can then push it to your desktop Adobe Photoshop.
As for Photoshop, its a very powerful program that many think they know how to use. There are multiple ways of adjusting various parts of your file. But what people don't realize is how much you can integrate something like Adobe Illustrator with Photoshop and then use your design in a page layout program like InDesign, etc. As a professional graphic designer and photographer, I've interviewed many creative candidates to fill job positions in my field of work. The one thing that I see the most is that they really don't know how to maximize the software. Although the end product looks great, I ask the technical questions to the candidates and investigate if they used the program the most effective way. I would sometimes look at their design file and study it. Many candidates only know the basics and sometimes its very hard to find an artist who really knows the ins and outs of Photoshop and how to maximize the creative tools in this program.
And you're right, Photoshop is not the "end all, be all". There are tons of cool touch apps out there (i.e. Procreate, Paper, etc.) that are great for anyone's creative workflow.