Traditional phone service relies on the PSTN (Public Switched Telephone Network), which is the federally run network that connects all landline-based phone calls. Traditional phone calls use analog data, which is relayed as electrical pulses. It is difficult to send analog data over a long distance without losing call quality, so there need to be lots of transfer points for an analog call along the way.
VoIP uses digital data, and it is easy to send digital data over long distances without stopping. VoIP only uses the PSTN if a VoIP caller is calling someone who does not have an Internet phone number. Users are able to use VoIP if there is a WiFi connection already in place, whereas traditional phone users would need to physically connect to a landline for service.
For these reasons, the FCC has largely left VoIP alone. However, as reported by Bloomberg BNA, the FCC is looking to add more regulations to VoIP in the near future because VoIP has become such a popular choice for so many landline phone service customers.