You run into a ton of problems when driving. People hate problems - When I go to the grocery store, I expect to find what I want and get out of there within a reasonable time. Sometimes, things don't work that way. An item may be sold out. The store may be understaffed and I might be late by an hour. This will generally make a lot of people unhappy and angry.

Driving is not without problems as I said before. People who speed becomes an inconvenience to many other drivers. It's easy to feel anger when someone becomes an inconvenience to you so you become an inconvenience to others as well, perpetuating the problem. This is one of the reasons why we have laws limiting speed and other similar behaviors like tailgating, illegal turns, and yielding so you don't cut anyone off.

So what can we do about it? Nothing. There will always be assholes everywhere. Your response to their behavior can ultimately change how things turn out so try to practice some of that if you can. You can't control other people's stupidity but you are 100% in control of your own.