Becoming a phone company was never in their best interests. VOIP has been looking for the killer app for 10 years. Unfortunately, everyone who does it winds up competing on cost.
Why? Because the telephone has had over 100 years of innovation. So every VOIP company recreates the wheel and sells it for less than the telcos or PBX companies by making it free or almost free. In the end cellphones will win out. The only thing people seem to care about VOIP for is games. The rest of the time they're just as likely to pick up a cell phone or land line.