No hose clamps?

My installer did not use hose clamps when fitting black 1/2" polypipe with a torch to the nylon tees and elbows when re-designing part of the sytem after a home addition. Other zones that had previously been installed with 1" black polypipe have hose clamps at each fitting. I have noticed that a few of the elbows (connecting to the heads) and tees on this redesigned zone have been leaking and I remedied by replacing the overtorched section of pipe and installing hose clamps. Is it a neccessity to use hose clamps on 1/2" pipe and if so, am I asking for problems down the road with the remainder of this zone which is clamp free? If it makes a difference, this zone uses Hunter pro spray heads with the lateral line leading from the valve going directly into one of the heads and then branching off from there which has caused some pressure differences amongst the heads. The pressure regulator I installed on the jar top head did not make much of a difference regulating the pressure. BTW, the installer refuses to change design and I was hoping to clarify the clamp issue before discussing payment. Any help would be much appreciated.

Barb fittings CAN attach to the pipe fairly tightly, but I have ALWAYS used clamps on them anyway. They may be difficult to remove, but they can still leak a little bit under pressure.

1" poly gets clamps always, anything under that is usually just pressed over the barb. Think about it, in the field you are only charging the line under flow conditions and only when you WANT it to get wet (duh) - the 1/2" won't come apart, especially buried, and worrying about leakage (while watering) is somewhat... silly.