Keeping online servers up and running costs money, so when the player count drops below a certain line, they are usually shut down. Ubisoft has now announced that they are doing just that on November 19 for a number of games, some of them rather successful in their day, and there's a couple of more recent titles as well particularly in the Just Dance franchise.
All of these games can still be enjoyed offline after November 19.
Just Dance 2018
Just Dance 2017
Just Dance 2016
Just Dance 2015
Just Dance 2014
I Am Alive
Tom Clancy's EndWar
Splinter Cell Double Agent
Assassin's Creed II
Rayman 3 HD