You should also keep in mind that everyone dosen't owns a high end machine or even a macbook. I have 4 machines at home , maximum specs are 2.5ghz with i3-4gb , and I guess this should be sufficient for running chrome alone , well atleast theoritically. In reality , chrome starts being unresponive , crashing tabs and stuff occurs beyond opening tabs beyond 7-8 and flash player crashes more often. Anddd , firefox is sure late to start ( a longer startup time ) , but idk how it manages to sustain itself throughout. In one of my machine , I have arch installed with bspwm as WM ,and firefox takes about 150-200 mb only ( when I'm aggresively testing it ) , with 7-8 tabs. Chrome , well ...