Just how much of a middle finger can they give to users before people wake up and move to Firefox? There was a time Firefox had some performance problems but that time has passed, it works every bit as well as Chrome does now, if not better.
While Chrome performance is obviously better for browsing, somehow opening DevTools makes it work much slower.
As for casual user, installing ad-blocker makes web browsing way faster.
If you leave Disable Cache checked under the network tab, the web will be substantially slower with dev tools open. This is (likely) the default setting, because it's important for testing.