The inability of others to make left turns at a light without coming into my lane is a weekly (at least) reminder of the carelessness and incompetence of those around me, and why I'll never lose all of my misanthropic tendencies. Is it really so hard to gradually flatten the wheel throughout the turn, rather than taking one sharp stab at it?
More understandable, but also more inconveniencing, is someone stopping the flow of traffic to make a left across several lanes to get to their destination.
It also turns out that left-hand turns are bad for the planet without providing compensating utility. From this article on smart logistics (emphasis mine):
UPS began to study ways to maximize shipping routes to limit time idling and save fuel, getting deliveries there faster by learning optimal shipping routes. ORION is a 1000 page algorithm that can learn shipping routes and use that knowledge to find inefficiencies and streamline the shipping and delivery process.
One of the earliest interventions was doing away with left-hand turns wherever possible. UPS drivers knew this trick already, but the algorithm was able to prove its effectiveness. Utilizing data from GPS, driver habits, and more, ORION was able to save 10 million gallons of fuel annually while eliminating 100,000 metric tons of CO2 emissions and saving up to $400 million in shipping costs by the end of 2016.
