in cache its harder for the average nontech person to access a cached video outside the website. Additionay in cache it’s considered a temporary store to help aid the service than a permament one.
When you download a video on Youtube it is probally against their terms of use while doing the same on Peertube seem widely permited by the playform based on the license the user uses. There are fewer Peertube videos that dont allow downloads then do.
With that said, a concerning amount of them have unknown selected as their license. So its hard to tell most of the time when its ok with the creator to download and if their ok/cool with it.