Why do we even bother forecasting weather more than 48 hours in advance? Is there any point to it at all?

9 days ago, I started watching the weather because a massive heatwave was beginning to set in around Chicagoland and I wondered what might be in store for my day at the Pitchfork Music Festival (tomorrow). 

When I first looked, the forecast said it would be 98°F and sunny with no cloud cover. This, of course, meant it would be well over 100° with heat index. Joy. Great way to spend an outdoor festival. 

A couple days later, I saw 96° and sunny. Still not ideal, but a couple degrees cooler. 

The next day, it was forecast for 92° with some cloud cover. 

A while later, it was 88° and a chance of rain. 

I gave up looking until yesterday when I saw it was forecast to be 75° with a 50% chance of thunderstorms. Still basically the same forecast as I saw today.


Kind of an extreme shift from what it was supposed to be when predicted a week and a half ago, eh?

Again, why do we bother forecasting weather more than 48 hours in advance?