You can understand it but you can't interpret the value. How many movies is a CD? Or a DVD? Or a 1TB SSD? Or even Avatar in 3D (presumably not 1)? How many movies have even been released in total/last year?

The number awes non-tech savvy folk but it doesn't really inform them of anything. You could just as well write "more movies than you will ever need".

And besides that, I personally think that news should try to educate folk. I'm completely fine with a comparison in the article. But why in the headline?

Not really. A 4K movie means nothing to 99% of people. Is it 4GB? 40? 400? How many can my phone hold? Or my computer?

This only makes things more understandable if you use a point of reference that everyone you're talking to is familiar with. The fact that they had to then explain how big a 4K movie is in the article clearly shows that even they know that this doesn't help people. It's just a big flashy number.

Just for context, I'm a writer, I understand the point of using these abstract measures to give a frame of reference. But in this case, just giving the capacity in GB/TB would have been easier to understand. It just wouldn't have been as sensational of a headline.