They will on a big screen, even if they aren't "aware" of it. Guess it depends on what your project is and who your clients are, go figure.
It would seem a bit of overkill to use a Scarlet for a youtube video- then again there's that whole 4k youtube thing...
Interesting study by Nielson though that finds that of people who own HD televisions, only 13 percent are watching HD programming.
http://paidcontent.org/article/419-nielsen-finds-small-minority-of-viewers-watching-true-hd/
And before everyone jumps in and says 'they will on a big screen', very, very few here will ever have anything in a theater, I'm not saying this to be harsh, it's just a reality. Don't make the mistake thinking that having a Scarlet or Epic will gain you anything in terms of commercial appeal for your project.