Hoodies are popular in the UK because of the widespread use of CCTV in all towns.
You shouldnt ride a bike with a hood up, it restricts peripheral vision.
Shoulder injuries are caused my transfer of impact from an outstretched hand. When used properly, a shoulder can take a lot of direct impact (see rugby and US football). Padding may reduce direct impact a little but it wont prevent any injuries at all.
The most common injuries are abrasion (called road rash). I think there would be a market for anti road-rash cycing gear.