I just don't think it's a problem these days for many people. I have a 2TB drive with several 1 TB ones lying around, quite cheap. I can understand not wanting to have people who don't have that benefit or internet speed to have to download them, but at the very least offer it somewhere. DVDs are cheap to produce these days as well, but it's not like publishers bother with most pc games these days on a wide level.
The big problem is they usually aren't very careful or elegent about it either. They just compress to absurd levels, comes off as laziness which is an incredible shame. Especially given the amount of time and budget that goes into the cutscenes.
For the amount of time you actually see them compared to the rest of the game, it's really not worth it, IMO.
I have unlimited internet, but not everyone does -- 30GB is an awful lot for some people. Plus my connection is only 1MB/s, so 30GB literally takes over 8 hours for me to download.
Plus, I have a 2TB 5200RPM, a 640GB 7200RPM and a 120GB SSD, so space isn't really an issue for me either, but some may just have an SSD.
Like I said, if you want to add a mod, that's cool. Or maybe they could have a high-res video pack, like Sleeping Dogs has a high-res texture pack. But I absolutely do not think they should make 30GB downloads a standard.