so I have a firetv stick, a chromecast, both play youtube hulu disney+ etc, they're each like $30~$40 dollars, I thus have never had the need to buy a Roku stic

so I have a firetv stick, a chromecast, both play youtube hulu disney+ etc, they're each like $30~$40 dollars, I thus have never had the need to buy a Roku stick, why do I need one and why does this youtube-tv-app matter?