Protip: New on the job and want to establish a reputation quickly? Find the most common path and fire a profiler at it as early as you can. The odds that there's some trivial win that will accelerate the code by huge amounts is fairly decent.

Another bit of evidence developers rarely profile their code is that I can tell my mental model of how expensive some server process will be to run and most other developer's mental models tend to differ by at least an order of magnitude. I've had multiple conversations about the services I provide and people asking me what my hardware is, expecting it to be run on some monster boxes or something when I tell them it's really just two t3.mediums, which mostly do nothing, and I only have two for redundancy. And it's not like I go profile crazy... I really just do some spot checks on hot-path code. By no means am I doing anything amazing. It's just... as you write more code, the odds that you accidentally write something that performs stupidly badly goes up steadily, even if you're trying not to.