No. They are not strong enough, and using them as an anchor point prevents them from being moved.
Chains with chain binders or ratchet straps.
Substantive restraints are procedural restraints used when consulting the US Bill of Rights. Substantive restraints are not usually physical restraints.
I'm not sure if you mean the extreme restraints website or if you're talking about restraints in general. The extreme restraints website would be used to shop for restraints. The extreme restraints are used in sexual play; if you're into that sort of thing.
The reasons would be medical or police related. Medical restraints are used with the goal to protect the patient from injuring himself and the police restraints are used to protect other people in the hospital from a potentially dangerous patient.
In everyday life, we use seatbelts in vehicles and restraint bars on roller coasters to keep us safe. Restraints are also used by police officers and federal agents to restrain criminals, and by criminals to restrain victims.