There is the temporal bit, a TV show ad hits all viewers at the same time and on a particular date so you can put time specific information in it. And there is a diffusion bit, you can spend $40,000 for your ad across all videos that are rolling with > 1M subscribers so your ad money hits a bunch of different people rather than one person.
If Google could convince advertisers to pay more for advertising, they could compensate their content creators more. But they can't so they don't.