it turns out you make the most money following the lowest common denominator.
The lowest common denominator is one PC in a house, and not all gamers live alone.
There is no real set standard on how to support additional players.
One standard has existed since 1998 when Windows 98 added USB gamepad drivers: DirectInput. Another has existed since 2005 when the Xbox 360 came out: XInput.
From a game design perspective, the LCD is the game designer has no restrictions beyond the hardware. But if you tell a game designer to design a game with local multiplayer, that is a restrict beyond the hardware, which wouldn't need to be addressed if you just let them turn it to online multiplayer.
But if you tell a game designer to design a game with online multiplayer, that is a restrict beyond the hardware, which wouldn't need to be addressed if you just let them turn it to local multiplayer. It is a restrict because it requires the user to move to an area where wired broadband Internet access is affordable and/or buy an additional PC and an additional copy of the game for each additional player.
Simple example: poker. How can you ensure each player can only see his own hand, and nobody else's?
I see your point about games with intentionally limited information. But there also exist games with intentionally unlimited information that must propagate instantly. Simple example: karate. How can you ensure each player sees each punch and kick as it is thrown, and not 200 ms later? How can you ensure each player owns a gaming PC, as opposed to a PC with integrated graphics more suited for word processing and Facebook, and a wired broadband connection, as opposed to satellite or cellular broadband or dial-up because the user lives in an area without cable or DSL or fiber?
Board games are relatively cheap to make, so you can still money making and selling them (and thanks to wear and tear, there's a market to sell the same old game over and over). Video games do not share that luxury.
By "video games" do you mean AAA games or indie games? I was under the impression that an indie game could be developed and brought to market on not much more than a board game budget.