Knowing how it works is extremely useful. And if you know one it's trivial to get to know another, like ARM as an example.
I haven't actually written a line of asm in last few years but when you are thinking about performance you must be able to understand compiler output. And that I have been doing a great deal. You simply cannot make well performing code without that knowledge.
You can always say that in modern desktop performance does not matter, but you cannot say the same in mobile space. There every single watt counts if you want to increase your battery life. Because when the CPU is idle they can pretty much shut the whole thing down for a small while.
I haven't actually written a line of asm in last few years but when you are thinking about performance you must be able to understand compiler output. And that I have been doing a great deal. You simply cannot make well performing code without that knowledge.
You can always say that in modern desktop performance does not matter, but you cannot say the same in mobile space. There every single watt counts if you want to increase your battery life. Because when the CPU is idle they can pretty much shut the whole thing down for a small while.