For me, it's important to have a 1:1 copy for situations in the future. I'm young(er) now, but maybe one day I would want to share these games with my kids or something. Sharing a copy that isn't exactly the same as the original in and of itself completely eliminates the possibility of whoever I share it with having the same experience that I did. Obviously, it can be argued that there are no fundamental differences between a 1:1 and a trimmed Wii game, but based simply on principle I'm sure you can see where I'm coming from.
There's also an historical appreciation behind making 1:1 backups. For example, in the not-to-distant future, I can see mechanical media such as hard disks, CD's, and DVD's disappearing entirely. If a 1:1 copy of the original disk is maintained, it can serve as an educational exercise for future intellectuals. "See little Timmy, back in the day when everything was so slow, data had to be aligned properly on disk to reduce seek times, necessitating the need for padding data." Similar to, do you remember the last time you defragmented your hard drive? I don't (I have a SSD).
Finally, if I have a 1:1 copy it (should be) relatively easy to compare it against the original to verify it is a clean rip, and it will allow me to trimmed, modify, hack, etc. it in the future as if I had the disk right there. Doing the same is not always so easy with trimmed or modified data because who is to say the data in my trimmed version matches the data in your trimmed version? Especially when each were potentially created at different times, locations, or using different tools.