Why has this not been added as an option still? 

To have to rely upon remembering to always attached the T&C via QB and sending just seems archaic and that there is a good chance it could be missed.

Adding the T&C file each time through QB also seems as though it would add to your ultimate file size since they are stored in QB as well would it not?

I sent in a request to have this feature added and maybe the only way to get it accomplished is to send a request regularly.