fansub groups – put OP and EDs in separate files!

Why do most fansub groups (Anime) include OP and ED into their encode, into their release file?

I don’t get it.

I love those who use separate mkv files, linked and with chapters.

One saves a lot of disk-space, bandwidth and download time.

Also, one who does not want to watch OP and EDs does not even have to download them,

one who does not want to archive them just leaves them out.

I skip over OP and EDs now anyway. Definitely if I watched already.

Do you prefer them to be in? Hard coded?

Or do you agree?