We do allow it. I pointed out right at the top the number of Blender users vs. Maya users. You can download Blender for free right now, either from the website or through Steam.
Left click to select is now the default in 2.8, and going back to 2.6, it was configurable. Now that the left-click argument has been shot down, I'm waiting to hear what the next significant complaint about the Blender UI is.
As I've pointed out in another comment, the 3D industry is full of professional software with "unconventional" user interfaces (eg. Zbrush, Syntheyes) that don't have a lot in common with other 3D software, let alone desktop applications in general. Those expensive packages are used by professionals who occasionally bitch about the interface, yet they still manage to produce astounding works of art with them.
I'm a rubbish 3D artist. But I understand it is because I'm not prepared to put in the amount of work required to get to a level where I'd like to be. I don't blame my tools.
I think your comment is a little disingenuous; I never suggested that only "good artists" understand how to use Blender. Like being a good programmer (which I am also admittedly not), becoming a professional 3D artist is a 10,000 hour (if not more) kind of problem, except for those with extraordinary talent.
The reason we hear these comments so frequently about the Blender UI is that it is free, so many people download it, and when they realise that it will take more work than they expect to become proficient, they take they easy way out and blame the UI (IMHO).