They don't. The local CATV company has fewer than 500 customers per node. If by some miracle every customer had their TVs on and every TV had a different show playing, then they would be in trouble. However, even with VOD and Video Re-Do, it's going to be rare for there to be more than 200 different video streams to be requested. By making certain the number of customers does not greatly exceed the total bandwidth they could possibly select, the CATV company can avoid such issues except in very rare cases. I doubt many people will complain if it happens once a year, or so. The odds of it happening to the SAME customer again and again is extremely low.