P2P is now slower and less reliable than conventional CDNs. This is a combination of bandwidth becoming cheaper, CDNs getting better (more locations, more peering, etc.), reliable always-on desktop PCs going away, etc.
P2P doesn't need "always on" boxes in large scale live stream scenarios, which is one of the use cases where it works best. I think we'll see a lot of growth in hybrid P2P/traditional CDN in the next couple of years.