I suspect it's not some nefarious plot from Mazda to make more money. Back when that switch was spec'ed out for the car they ordered or made X amount of units, enough to build the expected amount of cars they produced using it plus whatever they thought they would need as spare parts over X time. Remember, they didn't sell nearly as many CX-5's as they do now back then so the anticipated amount required for repairs wouldn't be all that high. Since they turned out to be failure prone as they age, as evidenced by the TBS, that stock of switches would get used up faster then anticipated. They likely only have the whole assy at this point since it's not as likely to fail and they already have the switch installed so that's the only stock left. It would be nice if they would make a run of say 500 replacement switches, but the odds of them doing that is nil since it would be very expensive just to support some 10 year old cars.
The reality is it's not just a Mazda thing. I was in the used audio business for years and ran into that sort of thing fairly often on complicated older units that they didn't sell a lot of. I can think of one turntable manufacturer that used a small plastic part in their arm lift mechs that when it wore out the arm wouldn't return at the end of the album. They got old, hardened and cracked off. After 10 or 12 years that simple piece became unavailable once the stock ran out, so 10's of thousands of turntables wouldn't work properly anymore, at least the return mech wouldn't though you could still play records manually. I only mention that one as I thought about it after I got my 3D printer and now I could make my own as needed. It's actually sort of interesting, a lot a parts for all sorts of devices that were long out of stock are being printed since the cost is so low to make them in small quantities now.
So the bottom line is devices age, the parts become unavailable and devices which are 99.9 percent functional get scrapped for the lack of one part. As a guy who has 20 year old Yamaha motorcycle I'm familiar with the problem, and have had to improv some stuff to keep the old girl running.