Why nobody else tried offering an existing solution to a new market? Is that a serious question? That exact thing happens all the time and has made many companies very successful. Hell, the site you're on right now isn't exactly revolutionary (user-content link aggregator with commenting system), but it found a target market in technically minded people and it has brought value to those people. Would you ask why people use Hacker News instead of Reddit or Digg?
And I don't know if they did develop their own system or are wrapping an existing VOIP solution, I didn't see it mentioned specifically.
If a new site opened up that offered exactly what Reddit does, but wrote their own code from scratch, (and charged), I would also ask what they're bringing to the table over Reddit, what features they have that reddit doesn't, and would criticise them for not reusing old code that did what they wanted if they couldn't show me any better features.
I guess I'd ask again, do you critique Hacker News for this?
It is definitely not a new idea to reuse existing ideas, even if you don't reuse existing code, to provide previously unserved/underserved markets with already existing services/products, nor is it a new idea to charge for it. I honestly don't know what you're getting at. Do you think they should provide this service for free because others do? Should customers just be smarter and know that Google Voice exists? What exactly do you find is wrong about this situation?
And I don't know if they did develop their own system or are wrapping an existing VOIP solution, I didn't see it mentioned specifically.