I challenge that. That it was done is as much evidence that it was doable as that it was required.
It is also a bloat race. Web pages are getting increasingly complicated. With very little benefit to end users. I'd wager a growing number of the cycles and network requests are going to tracking, nowdays. Not to mention the ui language doing more and more contortions to give us a page that could be much more succinctly described.
None of this is to say I want it stopped. I just have a feeling of concern that this is leading to an ever increasing march to faster and faster machines to do basic work.
Almost every modern device running a browser has multiple cores, and that trend is almost certainly going to increase – so it definitely feels like allowing a core part of the web platform to expand across cores will be beneficial.