I wonder what else humanity would have done with those 100 billion hours if it were not for Netflix.
In the old days? Back-breaking work that's no longer necessary or efficient. In the slightly less old days, probably socialize. Nothing super productive or world changing I assume. I would also guess that a lot of these hours are spent sleeping rather than actively watching. Most people I know put comfort shows on to help them fall asleep these days.
People worked for themselves and did what they needed to survive and live how they wanted, and doing more beyond that gave worse and worse returns that eventually people will stop for not having much value. Chopping 5+ years of wood ahead of time gains nothing because without a ridiculously large building to store it in it, which also requires more maintenance, will rot and lose energy and become less valuable over time. There is no point in making a lifetime's worth of your own clothes now if it is just going to get eaten by moths and fungus after being stored for 10-20 years. You are only going to get slightly ahead to head off bad times and then stop producing after that.
One of the biggest rallying points behind the 19th and 20th century labor movements was people wanting to return to the lower working hours that their grandparents and great grandparents worked living a far more subsistence lifestyle, and is how we came up with a 40 hour work week, which also assumed having time for the multitude of religious holidays and seasonal breaks in work they also enjoyed, and was still a mere compromise between the two lifestyles.