This will explain some things for you as to why. https://zooadmin.org/ZA/index.php?topic=1068.msg6307#new
There is a lot of work in making downloads that do not cause problems and it is for the designer to decide where they are. Especially those of us still making things. I know some of my files are hosted elsewhere without my permission and it would have been nice to have been asked, to say the least.
Some sites have given permission for where the files can go when they close. Many of the older files need updating before re-releasing them and that can take time.