The biggest reason is that there's so much more volume in organic search (80% of all clicks) vs paid search (20%), and the ROI on SEO is so high. There's also so many companies in the PPC space -- it's quite saturated. SEO is appealing to us because we think it's overlooked due to stigma.
SEO and PPC are really two very different games overall, but I have a ton of respect for people who are really good at PPC.