The holders paid to secure their wealth when they initially moved their funds to their wallet. It’s just that there isn’t an ongoing cost to holding it. But wealth that never moves is not beneficial. At some point they have to move it and pay a cost. 

I think that energy will become cheaper over time but also that bitcoin will become more valuable over time as well. The subsidy continues to shrink but Bitcoin’s value continues trending up while hash continues to rise along with it. 

Time will tell.