Scraping text across the entire internet is orders of magnitudes easier than scraping YouTube. Even ignoring the sheer volume of data (exabytes), you simply will get blocked at an IP and account level before you make a reasonable dent. Even if you controlled the entire IPv4 space I’m not sure you could scrape all of YouTube without getting every single address banned. IPv6 makes address bans harder, true, but then you’re still left with the problem of actually transferring and then storing that much data.