[eCa]

20 bytes per rule. While not a fan of the syntax[1], there’s the advantage when reading of seeing that rules are explicitly nested versus doing string parsing of rule definitions.

[1] In particular the significant space char difference between &. And & .

[hypertele-Xii]

Why does a website need more than one :hover rule?

[extra88]

At minimum, you'll likely have different effects for links than for buttons.

Component-centered design is very common so the styles for each component that would benefit from :hover may have its own variation on it, for the color differences if nothing else.

:hover is not the only interaction pseudo-class, :focus and :active can also be nested.