I was fascinated by both machine language and assembler, but two things make them too expensive. One is the obvious that it simply takes longer to write assembler (and machine language is orders of magnitude worse for anything more than a few lines), plus branching requires labels and those get hard to keep track of. The other is optimization. It's easy enough to memorize instruction timings for an 8008 or even Z80; it got beyond fun with the 68020; and I would say it;s impossible for modern CPUs, although I've never tried assembler for any RISC machine.

I liken it to hand tools vs power tools. A lot of assembler coding is the equivalent of hammering in nails or driving in screws. It gets boring fast, and it slows everything down for no enjoyable reason. As much as I enjoyed those old assembler days on those simple processors, they were not productive, and the satisfaction of seeing code run, first time, in an hour or two, beats days or weeks of assembler trial and error. Humans are good at thinking. Leave the repetitive boring error-prone stuff for computers.