Not to mention the extra resources being eaten by all this JS. When I leave a typical website with lots of ads and tracking open, I can see the energy usage averaging much higher in Activity Monitor on my Mac, even in Safari and with some basic ad blocking on.

I imagine folks serving up the JS have figured out ways around whatever simple blocking tech I have. If their JS wouldn’t eat up so much battery, I’d mind a lot less, since I leave tons of tabs open.