The original Transport Tycoon had 2 player support and it was very hard to setup (and keep up) the connection for the hours and hours a single multiplayer game would last. I think I’ve only used it once or twice on a LAN party.
So I’m not sure that multiplayer is must in this game. I’m perfectly happy with playing this game on my own, tinkering with all the transport lines, railroad signs, buildings etc etc. Adding multiplayer adds competitiveness and therefore pressure, which is not always needed in this type of game (same goes for Banished, afaiac).