OPCF49 opting out of DCPD in Ontario

The explanations on the form don’t make sense. “You cannot claim reimbursement from the driver or owner of the vehicle that hit your vehicle or from their insurer.”

So if someone rear ends my car I can’t ask them for compensation, even on my own? Doesn’t make any sense ! Don’t they have to pay collision to their insurance ? Where does that money go?

Or vice versa, I rear end someone and total their car, but because they don’t have DCPD, I don’t have to pay anything???

Can someone make sense of this for me please? How does the process work if you get into a not at fault accident and need to ask for repairs but don’t have DCPD?