In my old bakery job, we weighed EVERY ingredient in grams. Flour measured by cups can vary by like 20% depending on how you scoop it. That difference turns a fluffy sponge into a brick, no joke. I've seen home bakers swear by cups, but their cakes are never the same twice. For something as tricky as sponge, a scale is the ONLY way to get it right every time. Sure, you might get lucky, but why gamble with dessert?
Remember that time I tried to make a Victoria sponge without a scale? Ended up with something closer to a doorstop than a cake. Who even decided cups were a good idea for flour, when it packs down so easily? You'd think after a few brick-like results, people would just buy a cheap scale. But then, maybe the mystery of never knowing how it'll turn out is part of the fun for some?