I own 9 full face helmets (I like choices), and would never ride without one.
My favorite 3 are these. I wear my Bells the most due to the comfort of them:
Bell RS-1 "Born Free" The flake in this paint is AMAZING in the sun
Bell RS-1 "Steam Punk"
Both use the SOLFX Transitions face shield that self tints, so I never have to carry or swap different shields. When it's bright outside, they tint. When it gets dark, they are perfectly clear.
Shoei RF-1100 "Diabolic Revelation"
Two of my lids are modulars (flip face) and I will never go that route again except for the Shark Evoline series. My Scorpion EXO-900 fits well and isn't too loud, but it is HEAVY as hell and has poor airflow. I bought a Bell Revolver on a lark, wore it 3 times and promptly sold that horrible POS. LOUD doesn't even fully describe it. Plus poor airflow and felt very "open" inside which made me feel as though the protection wasn't there. This is why I don't spend so little on a helmet usually... you get what you pay for.
If it isn't SNELL certified and/or ECE certified, I won't even look at it. DOT in actuality means absolutely nothing. Individual helmets aren't even tested.. they just have to be ABLE to pass a very minimal test... in theory.
Anything less than a full face is good only for holding your hair in place. A high percentage of injuries occur at the front of the head.
I can almost get why some don't wear a helmet (I don't agree, but it's not my head in question), but if you're going to wear "a" helmet, why not wear a proper helmet???? Crappy cheap helmets lower peripheral vision and are loud and don't provide acceptable airflow inside... quality helmets don't have such issues. THAT's where a big part of the cost comes into play.
I also don't get the idea of riding long trips with a helmet, but not around town. As if an elderly cager in a 2 ton Buick won't pull a left in front of you on Main Street.... you're in as much, or MORE danger around town, even at slower speeds, than you are on the freeway.
Aside from the obvious stuff... I have had some insane stuff slam me in my face shield while riding that I would not have wanted to hit any part of my exposed flesh. Rocks, flying beetles the size of my thumb, dragonflies, getting caught behind sand trucks on the freeway being pelted with painful sand... you name it.
Wear or don't wear, it's your choice. But if you're going to own one, make it the best you can afford, and actually wear it. We own $20,000+ bikes with untold amounts of money in mods on them... why go cheap on something that can and will save your life?