Lets talk about the social aspects....

[RiyahArp]

...and why is that such a bad thing?

It divides FCs for one. You end up getting cliques based on who uses it and who doesn't, and it tends to make normal FC chat very silent. Also its hard to split focus since you might text chat with it or swap files, so you often keep the Discord window/app open over in game stuff.

and before that we had mIRC, msn, icq, aoe, yahoo msg etc. So yea. Only time i rly chatted (ingame) is when there needed some organisation or everybody who was online in the game. If not i used other chat programs to talk to my guild mates.

None of these really replaced ingame chat though. Even vent and teamspeak tended to be limited to raids; the culture was different then. Discord manages to draw people out of the game to socialize a lot more, during actual gameplay.