Actually many users do want immediate gratification. Don't want to wait for the media get transferred to the device and play. Also there is an issue of storing large file in your mobile device and delete it afterwards.
I am a Tonido user. I am not affiliated with them anyway
Instead of downloading media to your iPhone you can use Tonido iOS (https://itunes.apple.com/us/app/tonido-file-access-music-vid...) app to play/stream pretty much all the video formats directly from your PC, Mac or Linux (or) you can use the app to download the media and play with VLC.
At least with personal clouds you own your data. The real fundamental issue with public cloud is all the data at one place. When you have everything at one place it is prone for abuse.
It makes sense to invest in a company where the founders want to control the ownership. That really means the strongly believe in what they are doing. And other thing they should look in for founders is Perseverance.
I am a Tonido user. I am not affiliated with them anyway