With browsers, this wasn't really possible because you needed to give the full response after a single request. But running locally you can test all you want.
The problem is when you can't get everybody to agree on a standard API, so you resort to hacks that make it work ASAP that then lead to more and more hacks till we get the insane user agents of today.
If you were creating a new class of software where this could be an issue, what would you do?