Keno and Dice are not reliable monetary sources and are not comparable to baseball in that regard. Keno operates more like a money sink than it does a money generator and while some have made a net positive from playing it, that has not been the case for an unfortunate majority. Additionally, I think Keno and Dice make good in wars when you're blockaded and carrying money that you wouldn't want your enemies stealing. Gambling it on casino games yields either, a net gain which you gamble further or invest into your nation, or a net negative which your enemy can no longer steal.
Yeah it's not what PnW is about, ultimately, but I think it's a mechanic that serves a unique purpose in losing wars; preventing the enemy from stealing money + little bit of fun if you happen to win.