Remember, it's up to the individual uploader whether they wish to continue sharing their own work.
If their upload wasn't their own work but just something they acquired from from the Internet or another site, it can always be uploaded again by anyone who has it.
The problem is, how do we know?
Once the file has gone, we don't know the uploader, whether it was their own work etc.
Not wanting to step on toes, we can't really upload again to be told "that's mine, take it down" and cause friction.
Maybe we should put our names on the titles - Like Martin does - then there is no doubt.
I have the Jungle Cruise and the Frontierland BGM (mines the DLRP one which used the same BGM originally as DL or WDW) - both popular torrents looking at my share ratio for them

and I had those for years and long before I joined Mousebits (and, I think, well before they were uploaded here - they were amongst the first ones I found on the Internet) but without knowing who created them, it's not fair to put them back up.
I think some uploaders have had problems with others and have stopped sharing (probably an excess of PMs asking for stuff or stuff being sold on CDs etc, I don't know, just a guess) and have chosen to remove their files and stop sharing.
Maybe someone else knows a little more?