Yeah, I get that - if you're right handed, and using the mouse, WASD is absolutely natural for movement - it's where the other hand naturally sits. But, the primary reason for that is actually because the mouse is natural to use with the dominant hand because he mouse is used for precision work, so you want the most control. But when you're not doing that, you've got options.
I'll reveal myself to be an old fogey here, and mention that a lot of video games on computers historically used the arrow keys for moving - even predecessors to today's 3D games (Doom and Wolfenstein 3D being two of the major titles I remember from when I was a kid) used the arrows to move. Part of that I imagine being intuition (with minimal video game history to pull from, arrow keys meaning "move" were probably more intuitive, and I'd guess the other part being that the majority of gamers would be then handling the most intricate controls with their dominant hand (mouse aim wasn't a thing - in fact "aim" wasn't a thing beyond left/right 🤣).
Now, there's decades of games that use WASD + mouse "look" for movement, so I expect that's why people find it natural to go for WASD, and then "mouse attack" just feels like the obvious pairing. But they're a different style of game. As someone who uses a laptop, grew up on games that didn't use a mouse, and spends too much time thinking about Human Computer Interaction (and never believed my HCI professor when he tried to evangelize the superiority of the mouse for ALL interactions), I tend to notice these things, and spend (obviously) too much time thinking about why they do or don't work.
That all being said, yeah, control customization is a pretty typical way to deal with "there's lots of controls, and no two people are the same".