print design - Should in-house clients receive native files to make their own changes?

I am the in-house designer for a company that employs 8 marketing managers. These marketing managers are the ones that supply me with the lion-share of my projects.

However, more and more, the marketing managers are asking for the native files, so they can make changes to the materials I've created and use those files to create additional materials.

The issue I am having with this is, the marketing materials they are creating with my natives are absolutely terrible. What is troubling to me also, is they don't seem to care, in their eyes it's "good enough". They would rather create something fast and on the fly than have me create it.

Now I can understand the convenience for them, sometimes they need something fast, however the designer side of me is appalled that our customers are being presented with materials that look, quite frankly, terrible.

I'd be totally fine with this if I didn't work for the same company, but I do, and I have pride in the materials that our customers see. So part me would like to take a stand and say that all marketing materials should flow through me, but that would cause quite a stir.

Anybody else experience something like this?