IRC Channels and Programmers why?

Well IRC is known for normal people as and old chatting network that most think is not any more

well for programmers it is the best place to get live support specially on freenode network ! and if you go there you will find channels full of hundreds and thousands of users !

what makes IRC the best place for developers they could have used any of the modern platforms, facebook groups, google + communities or anything else ( iam not saying they are not used) but still there is something that makes IRC first choice for developers why is that