One difference from the past is that the games move slower, so a kid now can watch 2 or 3 slow-paced innings before bedtime, instead of 5 fast-paced ones. Watching a smaller portion of the game played at a slower pace leaves kids less interested in who won.
And as a parent, I'd be far more likely to let my kid stay up for another couple innings if it was to see the 8th and 9th instead of the 5th and 6th. And my son doesn't even bother asking to if he can stay up to see the end, he knows the game won't end until hours after he is asleep.
Another probably bigger one is that when I was a kid, postseason games on Saturdays and Sundays would be day games, so I could watch every inning I wanted to, no problem. Now they start at about 8:30 PM on those nights. If they even started weekend games at 6 PM ET now, a lot more young people could watch the whole game, instead of a couple innings.
I don't understand the idea that it's better to have to miss the end of the games, rather than the beginning. That is completely opposite to how I see it.