Why? Because they're junk and they don't fit.
Why don't they fit... well, there's a major issue with the placement of a pair of mounting dowels.
Below is a photo of an original equipment Bosch unit, Bosch p/n 0 311 400 012, for the RH front corner of a 940.
Note the location of the dowels within the (very skinny) red circle.
This is the Taiwanese Depo brand unit.
Now let's put the two next to each other.
"..... Houston, we'd had a problem...... "
Totally, completely, absolutely wrong.
This isn't just a problem with the RH Depo junk - the LH units are also stuffed up the same way.
The only way you can make these units fit (and fit badly at that) is by removing the longer dowel.
Even then, the fit is absolutely disgraceful. But it will have to do me for the moment, until I can get some decent replacements.
Unfortunately I bought these things on eBay a long time ago, and never really needed them until now, when I have to get a recently-acquired 940 wagon through the registration process, as the originals were cracked. So no chance of a refund.
So if you're thinking of getting a pair, remember this post. And be warned.