The risk of getting hurt is much greater without the belt.
Certainly. The law (that does not require a seatbelt on trikes) was made for three wheelers where the rider/driver is not enclosed in a cockpit and more likely to go rolling down the road in the event of an accident. In the case of the M3W I would always wear the seatbelt for safety and I also think a helmet is a good idea whatever the law may say.