I never said I knew why they were read-only and I never said the solution was simple. I'm saying it's a problem. And rather than simply acknowledging the problem exists you go out of your way to give Microsoft every out on why they haven't/shouldn't fix this. If anything its an opportunity for Microsoft to do better. It's too bad you don't seem to see it that way.
Microsoft has finite resources. Every feature they add comes at the expense of another feature they can't add.
The question isn't "Should Microsoft have implemented VBA on Windows Phone", but rather "What feature should they have not implemented in order to spend time coding, testing and security checking VBA on Windows Phone",
Or if you prefer to use the future tense "Should Microsoft introduce VBA into the next version for the small-ish numbers of people that want it, or should they add something else, like support for older versions of Excel documents?".