I wonder what is the thrill of playing casino games alone, would it be better if we had multiplayer and play against each other and gambling on games such as plinko, flip or wheel?
Casinos have long been using socialization in gambling. For example, online casinos have a chat for communication, as well as a ladder of the luckiest players and their winnings. I think casinos haven't quite figured out how to develop this to increase competition between gamblers (so that User #1 can see User #2's achievements and be motivated to replicate their success).
Casinos do have a multiplayer mode - it's any card game played by multiple gamblers.

Speaking of plinko, how do 2 players play it? It's not like online ping-pong, where you can control the ball. Here, the ball moves erratically and is uncontrollable. The only thing that could be added for "multiplayer" is a list of gambler's names to the right of the screen, along with the multipliers they've won and the winning amount. Accordingly, the luckiest players are marked with special attributes, such as crowns or stars.