You can’t just plug and play it. As soon as you introduce async you need to have the runtime loop and so on. Basically the whole architecture needs to be redesigned
It's this - asyncio is a nightmare to add to and get working in a code base not specifically designed for it, and most people aren't going to bother with that. asyncio is not good enough at anything it does to make it worth it to me to design my entire program around it.