I do this a lot, either youtube video downloader or IDM.
Is not like we download every single video we are going to watch AND if you have IDM, at the right top of the video there's a button, you press it and it starts downloading automatically. I don't see where is the waste of time in that. All it takes is 2 clicks and you got the video in your PC. Simple, fast and you have the whole video, not silly at all...
Unless you don't know what I'm talking about and you didn't know IDM and programs like that exist, it's ok.