Just brainstorming here:

Yes, they are hot, and they are heavy, but in any situation where there may be even a remote chance of conflict (riot, demonstration) they should be worn. They protest you from not just any enemy but any accident, heck, its not even e good idea to ride a bike without a helmet.

If the situation is dangerous enough for you to have a weapon, then it is dangerous enough to have a helmet.

Berets don't keep the sun out of your eyes, helmets do.

Berets are not worn in a tactical environment, if soldiers are not wearing helmets, they are wearing softcaps (what the army used before berets)
and these 'hide the eyes' more than a helmet would.

I think the europeans either have a beret fetish or are still having a hard time grasping the idea of camouflauge. I've seen pictures of foreign legion troops deployed tactically in Ivory Coast wearing thier flashy red 'target' berets. I don't know what they are thinking.

The 101st airborne and elements of the 82nd airborne make up a large portion of the troops in the gulf. They wear maroone berets (great targets).

Marines, in the area don't wear berets at all, they have softcaps which hide thier eyes moreso than helmets.

. . . oh, and a rock could injure you if you get hit in the head by a big or fast enough one. . . . good idea to keep that helmet on.