A potential problem with automatically switching player in some contexts, is that it might make it a bit confusing in those situations where the game can not automatically switch, or when the switch happens without the player realizing, depending on whether the player switch is local (not really a switch at all, you are just allowed to give commands to other companies' vehicles) or global.
If the change is local, you might be messing around with some vehicles belonging to company A. Your mind is then fully focused on A. Then you need to build some roads, and totally forget that the global context is still company B, so that the roads you build belongs to company B, not A as you intended.
If the change is global, you might be building a road as company A. Suddenly, a vehicle belonging to company B requires attention, so you do something with it, not thinking about the fact that by doing so, the game automatically switched player to company B. Then you go back to building the road, but you are now unintentionally building the road as company B, not A.
Both cases are caused by the game's player switching not necessarily aligning with the context switches in the player's mind.