Purpose of LDA argument in BLAS dgemm?

The Fortran reference implementation documentation states:

*  LDA    - INTEGER.
*           On entry, LDA specifies the first dimension of A as declared
*           in the calling (sub) program. When  TRANSA = 'N' or 'n' then
*           LDA must be at least  max( 1, m ), otherwise  LDA must be at
*           least  max( 1, k ).
*           Unchanged on exit.

However, given m and k shouldn't I be able to derive LDA? When is LDA permitted to be bigger than n (or k)?