PPC is working why do SEO?

PPC has a lot going for it and many businesses have built there business model with a heavy reliance on this approach.

If you fit into the latter category, there is nothing at all wrong with that. In fact, if you get a large a proportion of your business form the Internet, Seach Engine Marketing (SEM) or Social Media Marketing another form of Pay-Per-Click (PPC) are near enough a necessity.
Over the years you have probably improved your skills and grown your Click Through Rates (CTR) and been largely blinded form the steady decline in conversions. That was always going to happen as the Internet became more mainstream as indeed was Google maximising their potential take form the world’s businesses.
Today, any Competitive Niche that focuses on internet traffic is already forced by the increased Costs of Customer Acquisition (CAC) and declining CLV, or Customer Lifetime Value. The ones winning this game right now are wining customers across many channels such as  Organic,email engagement, bots, local advertising, events, etc and most important of all, they are joining up the Omni-channel experience to maintain a salient conversation as the potential customer moves between, store, call-centre, re-marketing, mail-shot, website etc.

Here is an important fact you may not have fully appreciated: The cost of your CTR with Google gets lower when a: you spend more, b. you have a better reputation, c. your SEO ranking is higher.
What this means to you is that not only are all those organic enquiries costing you  a lot less than paid visitors, but they are substantially reducing the cost of your paid for traffic.