It's also somewhat inclusive of Lunar New Year and Diwali. More broadly, it's a public recognition that not everyone celebrates Christmas to make it clear they're accepting of diversity.

Maybe it's the Canadian in me, but I don't wish anyone a "Merry Christmas" unless maybe if I specifically know they celebrate Christmas; I almost always say "Happy Holidays!"

When I was a kid, it wasn't entirely uncommon to get a big gift during a random holiday get-together.

But I think "holidays" is more of a generic retail term used to get people to buy more and feel less limited.