While I was reading aiohttp server documentation, I came across this 
Warning
Use add_static() for development only. In production, static content should be processed by web servers like nginx or apache.
Why cant we use aiohttp to serve static files?
Why cant we use aiohttp to serve static files?

You can use aiohttp to serve static, but you shouldn't.
Web frameworks like aiohttp are specialized in providing convenient API to create dynamically generated responses (like web pages). They aren't specialized in serving responses with most efficiency and security.
Servers like NGINX on the other hand are specialized in serving things. They can do it more efficiently (C code speed, multiple cores utilization, caching) and secure (protection from common attacks, IP filtering, etc.).
Since static files aren't dynamically generated there's no need to involve aiohttp in serving them. Specialized server will handle their serving much better. It's a common practice to delegate this job to them.
why cant we use aiohttp to serve static files for production?