Why do Wii games take so long to download?

It has become a serious pain for me downloading games from more advanced systems like Wii and PS2. It takes nearly a half hour most of the time and I have downloaded larger files for other things way faster in the past (Not from this Site). I understand that there is more to system games than there is handheld, but it is honestly pretty aggravating waiting nearly 30 or so minutes in between each download. I know you guys only allow one download at a time to attempt to avoid download back ups and site traffic, so I am not asking to allow more than one download. However I am asking why it takes so freaking long for Wii games and if it HAS to take this long. By the way I love the site and am thankful for it and all it offers, so not hating the site, just the download times...