I didn't say you need it, but it incentivized the development of those more efficient cryptocurrency technologies by providing a decentralized store of value in which the market could build trust in the interim period where proof-of-stake technologies were still being developed.
What I am saying is that perhaps proof-of-work coins actually bootstrapped proof-of-stake technologies, thus leading to more rapid development of cryptocurrency technology in general.
You may say that, but given that proof-of-stake coins should be able to easily outcompete proof-of-work coins on a purely technical basis, and yet they have not achieved that success yet in practice (although they are growing rapidly), it seems the overall market still disagrees.
What I am saying is that perhaps proof-of-work coins actually bootstrapped proof-of-stake technologies, thus leading to more rapid development of cryptocurrency technology in general.