The thing with defaults is that they are what a new user gets on first install. Professionals &/or those with experience can change it to a personal preference all they like, but new users need something they can utilise straight away. It is trivial to find people talking about how back-asswards the right/left click select is… especially when it is not consistently applied throughout the application.
However, if people are going to bring up the Sebastian video, here is it’s rebuttal:
0:10 - it’s beyond “not really that common”, it’s nigh on unheard of. Left-click select on the other hand is so common as to be a defacto standard.
0:49 - regardless of which click “misses”, something inadvertent is going to happen. Currently the 3D tool is moved (& may need to be moved back), in the case of left-click select a selection is made that may need to be undone. Missing causes issues regardless of which button is default and so is not an argument for or against left-click select as default.
1:10 - Incorrect. Box select allows you to select the point, not to mention it is a contrived example. I can probably count the number of times I’ve needed to select a point in Blender behind a widget I’m trying to use on one hand. The number of times left vs right click select gets mixed up even after years of use is so far beyond that as to be ridiculous.
2:20 - artificially difficult alternative mentioned. The easy answer is to do exactly what all the other ones do, which is to have a widget (you know, like those in the previous example) that one can drag back & forth. Or even just have scrubbing be a right-click & drag thing. Once again, his personal preference is stated as a reason for keeping something that is counter to most other software professionals will use. He states no reason at all why left is better than right other than that’s the way it is implemented at the moment.
2:40 - as above. Sebastian states that left-click select is bad because it is currently timeline scrub… which can’t be right-click because that is implementing select & drag… which is performed with a left-click & drag in the other applications editing video that set the standard some time ago
3:35 - He admits that, in general, a modifier is needed to select multiple faces to limit texture painting to them only… but whilst that is apparently fine & dandy for the general use case, it somehow is stupid to simply apply a mask using a modifier like done in every other software. I cannot recall when I last needed to select only one face for masking texture paint and holding shift never really bothered me given it is not really selecting any of the texture, it’s a creating a mask outside which I cannot paint.
3:47 - “that is very easy and intuitive once you learn you select things in Blender with your right mouse button”. Couldn’t have said it better myself. One needs to ignore the general standard of selection you use in other applications and even inside Blender for certain areas and just learn that Blender is different. And once you learn Blender is different to everything else you use, and even in some areas internally, then that becomes a good reason not to make Blender consistent with other software.
4:30 - It’s not a big deal to Sebastian. It is a big deal to the rest of us. Sebastian’s personal preference is not a good reason to violate standards in user interface design. It’s a good reason for him to be able to change it if he likes (and he can), but the defaults shouldn’t need one to unlearn standards simply because Sebastian (& certain core developers) have a preference for right-click.
4:50 - wait, you mean left-mouse allows you to select & drag corner points, just like one has to use right-mouse for in other places (like the example @ 2:40)? I thought this was a video demonstrating why right-click select was the better option… it appears he just undermined his own argument by showing how easy and cool it is to do that using left-click!
5:05 - this one made me laugh out loud. Selecting with the right mouse button is a good thing because selecting with the left mouse is separated! Hang on a second, what side is being argued for here?
5:50 - um, Sebastian is using left click to do multiple things and that is why we cannot use left-click to do multiple things? Ignoring the fact that being able to left-click tweak has not stopped other applications with masks from being able to work consistently & intuitively, this is not a reason for stopping left-click to be the default for selection! Sebasitan is simply demonstrating how things work currently, not why they are better than the suggested alternative.
6:20 - and here we get to the meat of the argument. Sebastian agrees we should use both left & right mouse buttons (and no-one is saying otherwise), but he feels it is better to stick select on the right-button for ergonomic reasons. No mention as to why right is better than left for this (other than that is the way Blender does it currently), but he feels the current way is better cos reasons.
6:35 - this applies in both directions. Those preferring right-click select can do this just as easily as those preferring left-click select now. The advantage of left-click select being that most people coming into the application and not knowing where the settings are & what they can change get the de facto standard they’ve gotten used to elsewhere and as applied in some areas of the Blender interface anyway.