Why is it best to use a prime number as a mod in a hashing function?

If I have a list of key values from 1 to 100 and I want to organize them in an array of 11 buckets, I've been taught to form a mod function $$ H = k \bmod \ 11$$ Now all the values will be placed one after another in 9 rows. For example, in the first bucket there will be $0, 11, 22 \dots$. In the second, there will be $1, 12, 23 \dots$ etc. Let's say I decided to be a bad boy and use a non-prime as my hashing function - take 12. Using the Hashing function $$ H = k \bmod \ 12$$ would result in a hash table with values $0, 12, 24 \dots $ in the first bucket, $1, 13, 25 \dots$ etc. in the second and so on. Essentially they are the same thing. I didn't reduce collisions and I didn't spread things out any better by using the prime number hash code and I can't see how it is ever beneficial.