Browsers are both multiprocess and multithreaded. The ability to run a few webapps without having your system drag to a halt is a feature that's important to essentially everyone.
Webapps such as? I have a 4 core CPU from 2014 (i7-4790K) and I can't recall that ever happening to me. Primarily because any modern OS will throttle crazy runaway threads to ensure UI responsiveness, so the system doesn't 'drag to a halt' as you claim.
Also honestly.. how many people are looking at CPU benchmarks to run browsers better? I'd wager a twenty that its mostly gaming nerds who are obsessed with CPU benchmarks. Then.. its also a question of knowing your audience. I'm sure they have a better idea of who their audience is than you or I.
"Primarily because any modern OS will throttle crazy runaway threads to ensure UI responsiveness" seems like you have a particular OS in mind, and I would be interested in hearing more. I do not observe that behaviour on Debian 9 (and other Linux distros), Mac OS X, and Windows 7/8. I regularly bring any of those to UI stuttering/freeze from various workloads. Webapps only really breaks the lesser ones singlehandedly though (most of my other systems are 4+ core with 32GB+ RAM).
>"Primarily because any modern OS will throttle crazy runaway threads to ensure UI responsiveness" seems like you have a particular OS in mind, and I would be interested in hearing more.
Sure. You should read up about thread scheduling and how an OS scheduler works. I don't think I can explain that in a comment, and I'd do a poor job anyway.
>I do not observe that behaviour on Debian 9 (and other Linux distros), Mac OS X, and Windows 7/8. I regularly bring any of those to UI stuttering/freeze from various workloads. Webapps only really breaks the lesser ones singlehandedly though (most of my other systems are 4+ core with 32GB+ RAM).
I don't observe that behavior. Just for fun I ran a CPU Stress test (https://silver.urih.com/) as I'm typing this comment. CPU pegged at 100%. Not feeling a thing... https://imgur.com/a/J0l9VaP
In Linux actual scenarios for stuttering/freezing are generally represented as a load average >1, and stuttering for me generally starts to happen when I get above 3 and I assure you no Linux system will work without observable stutter when you start getting into the 20+ load average range.
In earnest I have no idea why you tried to use a JavaScript based benchmark to support your point. Even after observing it the number of nonvoluntary ctxt switches barely even registered from baseline, probably from the variety of ways browsers do their own internal threading strategies. I could not see how to change that JavaScript benchmark to make it actually provide an interesting load on my system, so I'll just leave it at that.