Pikachu with Surf move?

Many people care because they like to 'catch em all'.

Raichu may or may not get it...we will know soon after the event starts (if Raichu can even learn it at all...off to Bulapedia I go). If we can we could make Pikachu/Raichu with Surf with event hats.

Not sure about TM but I evolved a shiny during the Xmas event and got a no hat shiny Pikachu with 'present'...so it is fair to assume that Surf will become an available move via TM.

All that said, if Niantic want to encourage us to have collections outside of the usable meta then they need to provide storage for these things

Nostalgia, it was a thing for some people in Pokemon Yellow. Just like most things in this game, of course it won't be of any use, but it's another trophy for people who want it.