Why does live streaming to mobile need a cable subscription when I can get the same channel with a HD antenna for free?

Was trying to watch the Thanksgiving parade at my parents. Didn't know they had a working HD antenna so spent an hour trying to cast and find a streaming source...

Then Dad said we do... I just needed to rescan the channels...

To get some money

It also takes up more resources to serve internet video stream instead of television broadcast because it's sent individually to every client. That's probably not the only reason but that's one of them.

@joas but tv stations are expensive build and maintain? I don't understand why if you're going to build them anyway (government funding?) why do I need to have cable in order to watch the same thing. Bandwidth is cheaper relatively speaking?

And I don't cord cutter argument doesn't make sense here cuz it's not like I want the cable TV channels, just local broadcasting that I could get anyway... assuming I buy a $20 antenna.

And actually with Roku, these channels actually have apps where you can watch shows on demand with ads similar to Hulu...

So app on Roku... Ok free
App on mobile... need subscription