TV has usually about 5-6s delay for live events, add a second or two for HD content. 1 minute delay might be in case of legal issues (where broadcasters are bound by law to add a delay) or some very convoluted video signal distribution.

Delay matters most in case of live betting and live score. There is whole industry around this, I am sure you've heard about bwin.com or bet365.com.

Delay matters when a twitch.tv streamer is interacting with their viewers through the stream chat.

Delay matters when multiple people are trying to watch the same stream "together", but end up seeing wildly different points of time in that stream.