Sometimes in life, ubiquity and commonality trumps design logic. Look at the qwerty keyboard scheme. At this point, there's so much momentum in that layout, there's really no point in trying to "improve" it for the vast majority of people. I certainly have no desire to try to rewire decades worth of muscle memory to change schemes. The "save" icon is another one that occasionally get hipster designers foaming at the mouth - a floppy disc, for pete's sake, which kids under sixteen probably have never even seen in person. The imperial system in the US was also far more difficult to dislodge with the metric system than many believed. The steering wheel, petal arrangement, and more or less standardized shifting levers are just another example.
Whatever benefit you think switching schemes gives you, there's an argument to be made that it may not be worth the short-term pain during the transition. It's tough to know where that boundary lies, I think. Metric vs imperial? Yeah, I'm sort of sorry we didn't switch. Changing the behavior of a car's shifter? Probably not worth it.