That would be an enormous waste of time. 99.9% of software doesn't have to be anywhere near optimal. It just has to not be wasteful.

Sadly lots of software is blatantly wasteful. But it doesn't take fancy assembly micro optimization to fix it, the problem is typically much higher level than that. It's more like serialized network requests, unnecessarily high time complexities, just lots of unnecessary work and unnecessary waiting.

Once you have that stuff solved you can start looking at lower level optimization, but by that point most apps are already nice and snappy so there's no reason to optimize further.

Sorry, I would word it differently. 99.9% software should be decently performant. Yes, don't need 'fancy assembly micro optimization'. That said, today some large portion of software is written by folks who absolutely doesn't care about performance - just duct-taping some sh*t to somehow make it work and call it a day.

People not paying attention on data structures and algorithms classes, or never bothering to learn them in first place.