We kinda have one in Canada. Well not exactly a curve, but it travels at an incline and then straight up.

The peace tower in Ottawa.

In 1981, a new inclined elevator was installed. It travels on a 10° angle for the first 98 feet (30 m), shifting its position horizontally 12 feet 2.25 inches (3.715 m), and straight up for the 60 feet 9 inches (18.52 m) remainder of the climb. The elevator car stays level at all times during its movement because it has a gimbal-mounted double frame.

WD40 is not a contact cleaner.

Diagnosing a problem at a shop is usually at minimum 1hr. Currently the shop rates are about $150/h

Book time on replacing the switch would vary from each make and model. But I would expect it to be no less then 1.0h

Then to take apart the switch, inspect what is wrong. Repair the corrosion. (Which is more then just spraying “wd40”). Test the switch. Verify the repair. Reassemble. Document the repair. I would expect 1.5-2.0 hours.

So your probably just about 4 hours, which is $600 plus taxes. With no one covering any warranty.

There is no way a licensed tech is doing that, if they can just replace the assembly. And have the repair covered for parts and labour.

There are multiple reasons why you can only buy things as assemblies.

Including having few parts to keep in stock. And some of these parts are not designed to be taken apart. Plus the labour to change the failed part of the assembly can be cost more then then new assembly. Assemblies are designed to reduce the overall cost. Especially with parts the rarely fail.

And as for you oxidation example. If you would take apart the column, clean the switch contacts. Charge the customer.

Now a week or year goes by, and the switch doesn’t work again. Either the contacts are still corroded or a spring broke inside. The customer would expect this to be covered. But since you didn’t replace any parts, there is no warranty. So either the tech or the shop does it for free. Or you loose a customer because they pay for the “same repair” again.

But if you replaced the switch, the odds of it failing again within the warranty period are much lower, because every component is new. And if something does go wrong, both the parts and labour are covered.

Now if you DIY, and don’t value your time. Then go ahead go for it.

Or if it’s an older vehicle and parts are discontinued, it may make sense to try and repair the part.