Lets talk numbers for a little bit. The DF screen does match the VT100 standard of 80x25. That is 2000 characters. For simplicity I am going to ignore a few telnet standards that might add some characters from time to time. Next we have to do the colors using the VT/ANSI standards that calls for a code of <ESC>[##;##m everytime the color is changed. Once again simplicity would be to send the color code for each character, which makes 20k bytes per screen, so far. We then need to include a small amount of control data, and some math, to arrive at 19.63KB per screen.
What graphics refresh rate did you want again? Does 8 FPS sound good? Would you want DF to slow down so it doesn't flood your limited bandwidth? Do you have any idea just how much bandwidth you actually have?
Of course that doesn't even count the work Toady would have to do to make DF send that data, and also make it know to hang around like a server just waiting for anyone to connect. Add to that many of us really want and use custom fonts and graphics for better display. Many of us still want even more display options, for example elves should look different from elephants.