Imagine you get a new phone with a new phone number, and you have a problem because some people still contact you on your old number. So instead of getting everyone to use the same number, you hire someone to take both of your phones and forward you the messages from each one.

Yes at some level it solves your problem, but it adds a lot of complexity which doesn't need to exist. Also now depend on someone in the middle who takes effort to manage, and might not do exactly what you want.