I kind of think seat belts should be required in rear-facing 3rd and 4th seats in golf carts, optional in front-facing seats, but recommended except when playing golf. The rear-facing passengers don't usually have a chance to brace themselves when something comes along to cause the driver to brake or turn.
I fell out once on a golf course when my ex-husband made a fairly sharp turn coming over a hill - I didn't know he was going to do that and executed, luckily for me (maybe not for him

) a perfect tuck roll over my right shoulder.
We (me and my SO, not the ex) just got back from TV, looked at golf carts to figure out what we want when we move down this fall and expect to buy a 2nd cart. For us, a 4 seater will be the 2nd cart choice, strongly leaning toward the Polaris Breeze. Even when the 2 (so far) grandkids visit, I would probably only put one in each seat along with an adult. Wouldn't trust little ones not to unbuckle it. As a rider and not the driver in the front seat, I felt safer being buckled up. The salesman told us most golf cart injuries in TV result from ejections, not from collisions.
As an aside, after I saw a post in one of the golf cart threads about gas cart emissions being 7 times greater than from cars, we are rethinking the need for a gas cart, at least if we are a 2-cart household. Think we will keep our current elec Club Car and add the Polaris. Probably will have another dedicated outlet put in, if research leads us to believe it's necessary or at least advised. An electricians or maybe ********* know the anser to this one?