You're framing the issue by saying that creation of IP happens for the reason of selling it later on. This is circular (IP wouldn't exist - it is a direct product of prootection), but I'll assume you meant that there'd be less investment in ideas in an environment without IP.
I disagree with your framing and conclusion. People work with ideas for the purpose of solving problems or satisfying interest that they have, not just directly commercialising the results. I write software in order that my business can operate in its environment. Mendelssohn was inspired to write the Scottish symphony. Free software authors have a commercial interest for their work because it increases their chances of getting good work, and the same applies for music teachers who compose and record, and literature professors who write, and scientists who publish.
Creating an ecoosystem that is oriented around direct commercialisation through the mechanism of IP cannibalises the innovation of people who solve problems and satisfying interest because of the extra weight of restrictions it places upon them. Many of the tunes in Handel's _Israel in Egypt_ were directly ripped from other work he had access to. That oratorio could not have been created in the current IP atmosphere.
Further, ideas benefit from network effects in a liberal idea space. Copyright hampers the exchange.
You equate IP with being all protection - this is misleading. IP is just one form of protection, one that is government backed. Consider Steam - a mechanism that furthers commercialisation of ideas without leveraging IP. The growth of models where businesses take responsibility for their own commercial model is stunted by the government protectionism offered in the form of easy copyright. This further fuels arguments like the one you've made. We look around us and see copyright everywhere tied up in ideas, and fail to appreciate the opportunity cost of the situation.
Without copyright you wouldn't have Hollywood, but you would have something else.
