Unused memory is not useless, it is just unused. If I want to pull up a guide on how to giggle the grables in my favorite game Grable Giggler, I would be very happy if I had unused memory which I can now use for my browser.
Also, smaller RAM usage generally correlates to smaller file size, which is very useful on computers with limited storage.
And finally, there’s also low spec gaming and accessibility. Minecraft, at least prior to the microsoft acquisition, was a very low spec game. I wouldn’t say it was optimized, but a game of minecraft took less ram than chrome. There was nearly no computers at the time which couldn’t run minecraft. At the time of minecraft’s early boom, kids were getting low-spec hand-me-downs, and so minecraft was one of the most open-ended games they could play. What I’m trying to say is that minecraft—and Doom for that matter—owe a large part of their success to low memory usage.
I personally think the change from master & slave was kind of silly, as far as I’m aware, it was a bunch of people with no background in CS who thought the application of the term to something that has neither race nor agency was an insult to black people.
But I digress. It led to better guidelines in the Linux kernel, which I think are useful. You should tailor the terms you’re using to the specifics of the task. If you have a master process that only has outward interfaces through the slave processes, you could use the term ‘director’ and ‘actor.’ if the master process is managing slave processes which compete over the same resources, you can use the terms ‘arbiter’ and ‘mutex holder.’ If the slaves do some independent processing the master does not need to know the details of, you can use the term ‘controller’ and ‘peripheral.’
Basically, use a term that is the most descriptive in the context of your program.
Edit: also, I don’t know why no one mentions this, but you can also use master/servant. Historically, there wasn’t a difference between servant and slave, but in modern days there is, so it’s technically different, technically the same.