This is one of the reasons why Proof of Stake was proposed as a more efficient alternative to Proof of Work while keeping the incentive for miners to keep their

This is one of the reasons why Proof of Stake was proposed as a more efficient alternative to Proof of Work while keeping the incentive for miners to keep their rigs validating transactions. Other cryptocurrencies such as Peercoin and Novacoin use both systems, but will shift to PoS only at some point in the future.