Jacket Why No Chest Armor

I'm not seeing chest armor in jackets. Why not? There are armors promoted toward off road bikers that cover back and chest.

I was actually thinking of getting one of those Motocross upper body plastic armor things those guys wear under a jersey when they race. They would offer actually more protection than the foam rubber in jackets, plus, with one of those, under a long sleeve "T" shirt, you may not have to even wear a jacket. ...Untill it gets cold.:D
I saw a "L" size pre-owened one in a local Bike repair shop. for $90.
Should have bought it Then!

The first reason that comes to mind is - to get the most effectiveness out of chest armor you need a solid chest plate. Its hard to make that work with a zipper up the middle of a jacket.

I can see a chest-protector being somewhat useful on the street, but I think that in most cases your hands and elbows would hit before your chest and soften the blow enough.

What I don't see the point in is armoring up your chest and not wearing elbow or shoulder pads, or even anything to prevent road rash on your arms.