PoW guarantees the energy has been spent to find the nonce. If one person had access to a perpetual motor, they could control the market. We assume everyone else would then have to find cheaper sources of energy to compete. If we take this to the extreme and energy were free for everyone then it would essentially become a lottery and the cost of additional mining equipment then becomes the limiting factor.

This energy-cost dilemma is required to required to balance the market. It’s also a highly speculative arms race incentivising mass misinformation campaigns to increase the value for existing Bitcoin owners.