The problem with things like 404 is then you need to differentiate between

"Hi, this is the application and the object/document/whatever you are looking for was not found"

with

"Hi, this is the server and the api endpoint was not found"

An API I use returns a standard apache 404 error page when the item you are looking up doesn't exist. If the API endpoint was renamed my code that consumes it wouldn't have any idea anything was wrong.