This is all in the same county, Fulton, and the northern part has voted to extend multiple times. The current Marta line stops about 8 miles from the top of the county.
Even other counties, Gwinnett and Cobb have recently voted to extend but that’s sort of a separate point.
My complaint was that Fulton county sales taxes support Marta, but Marta service does not extend all the way through the county.