Well, the team that's ahead can take say 38 seconds per play to run 4 plays. That's 2.5 min of the last five for four fucking plays, one of which is an out of bounds punt or a fair catch - usually (just boring shit). If forces the trailing team to use their time outs a lot faster. They will likely have one less possession during the "desperation period" when a victory is still possible, but you have to do everything right. They didn't have those fucking ten second runoff rules either. They weren't a bunch of pussies. Also, of course, they used to stop the clock when the ball carrier ran out of bounds or was forced out of bounds.
You could see a ball carrier run laterally or even slightly backwards to drag tacklers to the sideline in order to stop the clock. (A Texas tight end did that in the waning moments against USC, btw). He stopped the clock and possibly saved our comeback. Those kinds of plays were great play when they happened. These days the refs would consider the carrier downed, and they would signal the clock to start again, even though in my mind, the runner's forward motion had not really been stopped by anyone.
Currently these fuckers keep the clock running when an offensive player whose team is leading catches the ball on the sideline and is knocked out. It's just another case of creating so many gotcha fucking rules that the inconsistencies cheapen the "sport". If someone goes out of bounds, the clock should stop. We don't need an announcer explaining these ridiculous special rules, we need them talking strategy, which doesn't seem to happen anymore because they're so mesmerized watching the replay of the last 3-yard gain.
All this is done to shorten the game and, in general, the end of the game - the most exciting part - the climax.