Photoshop is simply "standard" and indispensable for many users. Even though there are now many alternatives for all possible applications, it is probably the proven Photoshop operating concept that holds most users to the bar. Programs like Affinity Photo or GIMP are too "unusual" to use in the eyes of many users just because of their alternative interface.
What makes us personally search for alternatives more often, however, is the restrictive Photoshop license, which makes it difficult to use on more than two computers. Because we always have small tasks on various (test) computers for which you don't want to install and/or activate a license.
In many cases even an online application can suffice, which does not require any installation but only an internet access. Already nearly 10 years ago we were enthusiastic about this 
Pixlr, a Photoshop clone in the browser.
But like so many copies of this copy, it still uses Flash, which is now hardly seen/activated in any browser. All the more we are happy to have stumbled across a new Photoshop Online Clone, which we like at least as much.
Photopea runs in many current browsers (without Flash), is free of charge and has been developed continuously for six years. The user interface and the handling are not only strongly based on Photoshop, but there are even many professional functions of the model. So layers, transfer modes or even specialties like layer effects and an area repair brush. Those who want to support the programmer can use an ad-free PRO version, which costs almost as much per month as a real Photoshop license.
Nevertheless, we are astonished again how much app you can download with WebGL without further installation in your browser.
;)