FUll disclosure: I work in the insurance industry and used to be a liablity adjuster, so the horror stories that I have heard weigh heavily on me.
I have a stellar driving history and a paid off 2007 Kia which isn't worth all that much, but I carry both comprehensive and collision. My main reason for carrying comprehensive: I live in a neighborhood with a lot of trees and I would be really pissed off if a tree fell on it and I was out $. I also carry a really low deductible ($100) because I've had to have my windshield replaced a few times and it sucks to pay for that over and over.
Collision: This is really important to me and kind of a soapbox. There are two reasons to carry colision and file through your own coverages if you are NOT AT FAULT for an accident.
1. The person who hit you had no insurance
2. The person's insurance company does not accept fault.
In both of these cases, you can file through your own insurance company. If the at fault party has no insurance, they will go after that person personally to recover your deductible and whatever they paid out on the claim. Insurance companies DO NOT want to lose this money and they have huge departments who will go to great lenghts to recover that money. If the at fault party does have insurance but they don't accept liability, your insurance company will go to arbitration on your behalf to prove their point (arbitration is a legally binding process that insurance companies use to mediate disputes. They do not take place within the legal system- for speed and to keep costs down- but the companies must abide by decisions). Companies have teams of specialized adjusters who go to arbitration to prove your case.
If you do not have collision coverage and one of these two things happens, your are OUT OF LUCK. Your insurance company is not legally allowed to take any of these steps unless they pay out on a claim. You are screwed and they literally have no recourse and can do nothing to assist you.
It is definitely more expensive, but I think it is absolutely worth it. FWIW, I pay $350/year for full coverage on my vehicle with a $100 comprehensive deductible and a $250 collision deductible. I also have very high liability limits (500/500/500). So, it is still extremely affordable for me to carry those coverages. If it was a lot more expensive, I probably wouldn't do it, but for $15 a month it seems worth it to me.