This was a fair point made by A.N.T. Likewise, ATL is a hub for DL/VS, and the more non-stop services there are to other US cities, the demand to fly via the hub is reduced to a degree.
Just to qualify the point I was trying to make: It's difficult to assess the degree of impact without knowing the ultimate destinations of pax currently using ATL to transfer. The other aspect is that new non-stop services create additional demand and growth to the US as a whole. In other words, the SFO service may simply lead to a redistribution of the present ATL transfers to SFO among other cities. If that were the case, there may be no reason to reduce the frequency of flights, but as always availability and utilisation of aircraft have to be considered.