Comcast can't even do symmetric speeds. I'm not sure what locations have thier best speeds but in my area, where they compete with the much more affordable but not as large coverage area offerings of fiber. The idea that they could offer even a signle gigabit level service to the majority of their customers is laughable.
I bet it did lead to a lot of confusion especially when you called up for 10GIGABITS and got offered plans in the Megabits with usage limits and overage fees and all kinds of complicated shit. I called in to cancel my service a few months back when i moved to an area with fiber again, they said "we offer gigabit too you know" and i was like , nah you kinda don't actually, but even if you did its like 3 times as expensive for just the download speeds.