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Nobody says it anymore
(startrek.website)
I've heard it explained that "hey" used to be more of an urgent way to get someone's attention, rather than a casual "hello" like it is now, so it sounded rude to some older folks.
Nobody expects online gaming to be a bastion of proper grammar.
People type in abbreviations when gaming mainly due to lack of time though... Much better to focus on the game than typing more than necessary to convey a simple message in those cases.