Sometimes you just want to highlight some text within text or within a list which means changing the background color behind the text to the typical bright yellow, green, blue... like in Google Docs for instance. It's for when you really need something to stand out like in a long wiki doc and bold or italic are not enough.

Concrete example: with have a wiki doc with our annual plan, essentially a big structured list, and some items have a target date and it would be quite beneficial to highlight them in yellow to be able to them at a glance.

NOTE: and friends are great but can't apply there.