God Dresden, you're a dumb fuck. Its sign language, not hand signals. Why should they have to use email when everyone else gets to call in?
The tty system is what used to be used, but its pretty old school. What you experienced was a video relay system (VRS), and its a multi-billion dollar industry. The government pays video relay call centers on a per minute basis to interpret for the deaf, who then call and annoy your dumb ass over the phone.