Hardware giveth and software taketh away.

My desktop today has 64 gigs memory, 12 cores. 10 years ago, it was 16 gigs, 4 cores. 20 years ago, it was 1 gigs, 1 core. 30 years ago, it was 16 megabytes, 1 core.

It cost me over $500 to upgrade my 4mb RAM to 16.

It doesn't matter if you're a kid, if you're not considering memory usage you were either trained by Google, became a developer through nepotism, or both.

It’s also possible to work on projects, or in languages, or on systems where resource consumption isn’t a high concern. I wrote cobol for sun and hpux and these big old systems had plenty to go around. Important software comes in all shapes and sizes, as do their developers.

My professional career has largely been web dev, where I haven’t really had to worry about resource constraints

It was quite a lot of fun in my university final project to be developing on a 6502 (NES) in Assembly and find myself working in a very restrictive environment. Likewise, when I was working with a powerful microcontroller, but still only 2k of memory and 16k of flash and not being able to use some libraries I typically do. I was left having to reimplement stuff on my own for my own purposes.

You could have said that 20 years ago. I've never needed to worry about clock cycles or cache locality, I don't even know how to measure cache misses in my code (I have a CS degree too). And the most consideration I give to memory consumption is whether to process data in a stream, or in memory.

It's absolutely the case that some developer still need to care about those things, but by the time I started my career 20+ years ago, it was possible to make a good career as a dev who didn't know how to work with computers at an extremely low level.

> how to measure cache misses

Run it under dtrace, probably others as well.