These are not "monopoly agreements" (which are illegal). If you actually read them, you'll see each one says it's "non-exclusive." E.g.
http://charmtv.tv/sites/all/themes/charmtv/pdf/comcast-franc....
What not offering telephone or television service gets you is avoiding the need to negotiate with the city for a television franchise. These agreements are usually stuffed with grab-bags for the municipal government (e.g. per-user fee, 5% of revenue off the top, offer XYZ public-access channels, build out to XYZ neighborhoods). All of this is imposed by the local government, not the FCC.
If you just want to run an ISP, build out where you think you can make a profit, and don't want the city to skim off the top, you can avoid that by not offering television or phone service. On the other hand, not offering television makes it hard to compete. People really do care about television service. I lived in an apartment building in Baltimore that had both cable and FiOS. FiOS was internet-only, because Verizon couldn't get a television franchise in the city. I found out I was the first one on my floor (of dozens of apartments) that had subscribed to fiber since the building was built 4-5 years before. All because people really love their television bundles. (There is a reason Google Fiber offered television service.)