Question in title may seem as trivial for some, but in this forum I see threads what show that it is not exactly clear topic for some (other) people.
Simple answer: there will be always something demanding higher and higher processing speed. Like simulations, games and so on. Detail level is actually still pretty much low.
When I bought my first ST, it was because I wanted faster computer than 8-bit one, at 3.5 Mhz. ST was almost natural choice then - it's price/speed ratio was then probably best. And yes, it gave me speed gain of about 4-5. Some 30 years later ST is very slow oldie. But it will be same with nowadays computers soon. We even can not imagine what will be possible with computers 10000 faster than what is now in mass usage.
There is lot of false claims, wrong statements, explanations circulating around. Some say that multiple cores are needed because one core replaces other, which must rest
That some CPU with 3x bigger cache is 3x faster. That you can encode video in Linux 4x faster than in Windows, because later is so inefficient. Well, latest one may be actually not that stupid. If user takes not care, it may be really that most of CPU time is spent on useless crap. But it is not Windows core what makes slowdown, or eats GBs of RAM. Windows 10 self eats about 1GB, but some services of it may much more.
In Win7 I just discovered that update service (while I disabled automatic updates) eats 25% of CPU time and 2GB RAM. For what - to look for updates. But probably there is more, what is not public, I guess. Is it stupidity, lazyness of MS people, or surveillance paranoia - will not go in it here.
Things are that you can have almost 100% CPU time, and most of RAM for your need in Windows. Just need to take care.
I say all it because some people in some threads here talk about very inefficient resource usage in modern OS, Win in first place. That simply is not true. All depends on you user. If you let them, they will take it over from you - advertisers, update paranoia and like. And even did not mention malware.
If you see slower work than usual, should immediately check in task manager, disable auto run of crap etc.
Speed is always welcome. I did recoding of great movie Heaven's Gate (over 3 hours runtime) with 2 core, little older CPU in 3 whole days. Some newer 4 core can do it 6x faster. But even Atari related things can go better - accelerated Steem is more accelerated. My primitive Win packer is still slow
Converting to STE high-color is still slow ... Claims that you don't need some high speed for usual tasks are just stupid. There is no such thing. Even simple WEB browsing is very demanding now. And will be more and more. This is how things go.
Video watching is where you need really high power - especially if want 4K with some modern codec. But even full HD with x265 (HEVC) is very demanding. But some still talk about watching DVDs. No thanks, that's just not enough sharp for me anymore.
Actually, today CPUs are very very slow for some things. Why they use thousands of CPUs in cluster by supercomputers ?
Of course, industry is one, who forces people to buy newer and faster computers periodically. SW publishers highly involved. But if you are not hardcore gamer wanting to play newest releases, you may save some money by simple checking of your config and disabling crap.
This is nothing new in fact. Stays for many of Atari people with mass storage too. They want lot of diverse resident SW like ACCs, extensions and like to be loaded even when using it not at all.
I'm not against GMO, I'm against that children play with fire.