I suppose I'd have to ask, what's your definition of "software development in general?" I'm certain it is useful for engineers at Apple working on iOS devices, at Microsoft working on Office, at Google working on Search, at Oracle working on their DB engine, etc., etc.
General software development, as in the 99% of code written, where the output asm is never looked at.
I bet developers at Apple developing the systen software stack scrutinize the code/asm. But all the application programmers that build on that ? Hell no.
Same with Office. How much of Office is performance sensitive ? And how much is GUI, auxiliary tools, wizards, function etc.
And same again with Oracle. Yes, they have a core DBMS which is super optimized, but in combination with that they have a *massive* Java eco system.
Do Java developers look at asm? Do C#, PHP or Flex developers? Do most C++ developers?
No.
If you need to develop optimized core software, yes understanding asm is a useful skill. But for most it is unnecessary.
Cheers