Because bandai's kits are for two groups of people. The serious builder who wants to paint, and for the kids who want toys.
I looked for those decals im surprised I could not find them, I could have sworn they had them. none the less Im going to give you this link here
http://www.gundamstoreandmore.com/gundam.html
Best place in the US for getting gundam kits, also
http://www.samueldecal.com/
for getting custom decals for your kits. Both are great stores,
EDIT: on Samuel Decal under gundam seed, in 1/144
so how long have you been building gundam? what have you built so far?