Not everyone can multi-task that well. I know at least 2 people, girlfriend included, that can't do anything when on their phone. They'll literally stop in their tracks when walking on the sidewalk or completely drop out of a conversation when reading / writing a text message. Let alone playing a game. I also think its a bit rude to play a game when in the company of someone else trying to have a conversation.
My wife can't multitask - she'll call me when she's walking to relay a two-sentence message because she can't type and walk.
I agree that it's rude to play a game when having a conversation with someone, but it's not rude at all for two people to be walking along and playing the same game.
