I feel like I'm taking crazy pills here

Team Chat = T
All Chat = anything else, come on

Mostly because it doesn't matter?

because Y is right next to T? it's like battlefield-style communication, brah.

Because Source engine games are like that.

Because T is for talk, and has been that way in probably hundreds of games, for decades. T is your primary talk button. Y is for friendly chat simply because it's next to T.

If you want, maybe we could do it the Battlefield 2 way and have the J, K and L keys be for chat, team chat and squad chat respectively... if you think that makes more sense.

Which it doesnt...

I always thought of Y as all chat, and U as team chat. That's the way it was in Quake...

there is no Y in Team, but there is a T, and a Me, and an A

T for normal and Y for team is how it's always been for me.
Will be solved when you can bind controls, since that's such an obvious thing dev will get to it.

T has always been ALLchat and Y always TEAMchat?

NeoTokyo (hl2mod)
bind "t" "say_team"
bind "y" "say"

Counterstrike Source
bind u "messagemode2" //teamchat
bind "y" "messagemode //allchat

Insurgency (hl2mod)
bind "u" "say_start2 //teamchat
bind "y" "say_start //allchat

TF2
U Teamchat
Y Allchat
http://tf2wiki.net/wiki/List_of_default_keys

ofc some crap games like mw2 tried to mess it up and changed it to T -> allchat and Y -> Teamchat lool

but still hl1/hl2 had/have the oldest and best teamplay games and they used Y for Allchat and U or T for Teamchat

therefore it leads to a lot of confusion and we simply need an option to bind keys.
thats it =)

ps:
old games only had T for Talk cuz they never knew TEAMS :-D
and not every has T next to Y :-P