You're quite right that the most important thing about the tool is that you can take the exported plain text result and put it in your code, web pages, etc.

But when it comes to actually creating the content, we want to provide the best user experience. Monodraw can be thought of as a drawing app which was designed assuming the output would be ASCII.

In my view, those aspects are orthogonal - you can have a hard to use tool that exports into a standard format or an excellent tool that produces proprietary files.