ISPs are not all equivalent. AT&T is a telephone company, and the telephone companies have always been considered common carriers, even when they branched out into providing DSL, and later fiber. Cable companies, on the other hand, are not traditional common carriers, and that status, too, has carried over into their respective Internet services.
Being a common carrier does not mean that the ISP cannot make a distinction between local and non-local traffic. This is not that different from charging extra for long-distance service, which was very common among the common-carrier phone companies before VoIP made most voice calls "too cheap to meter". It does mean that the ISP does not get to pick and choose the type of traffic they will carry, which should rule out things like DPI filtering or restrictions against running servers.