I've worked most of my career writing software to control physical objects. Nobody designs like this, it wouldn't even make sense.

The reality is that there are always competing interests. The Service team wants things to be easy to repair, but the Sales team wants it to be cheap and easy to sell, while Marketing wants it to never breaks at all. You can't reconcile all of those.

Sometimes engineers screw up. OK, often engineers screw up! But more often than not, functionality wins over everything and the engineer puts the sensor in the best place she can, given the constraints that she had to work with. Someone runs the reliability analysis and says that the sensor isn't likely to fail during the car's expected lifetime, so service isn't a big concern. Sometimes your specific car falls on the wrong side of that reliability curve, sometimes the engineer who did the analysis screwed up, or sometimes Shit Just Happens.

But no one designs things to be hard to service: that would mean it's hard to build in the first place and just take too big a bite out of profits.