This feels like an ipsedixit type post (and jfood uses that as a positive) but here goes.
Restaurants brew coffee to serve hot in the morning and it has a certain shelf life in minutes not hours. No the time has come where the choice is to pour down the sink or shove it in the fridge, let it cool and then recycle over ice. And the Einstein theory on all this is that you can charge twice as much for the stuff you almost threw out. Brilliant.
Why? When you fill the glass with ice it is about the same amount of liquid, so that answer is off limits.