For cakes, you often want less gluten (~7-10% protein) and that flour is not super common. All-purpose flour “works” but the product will be a little bit tougher because it a bit more protein instead.

That may have been true at one time, or it might depend on location. But at least in my area, cake flour is super common. Every grocery store has it. It's not generally worth the hassle of stocking it in my pantry versus just using AP, but when I'm trying to go all out I can get cake flour no problem.

Cake flour, any full-line supermarket will have it.