It is entirely possible that the popularity of Bitcoin (BTC) and Ethereum (ETH) has more to do with the fact that they are both big and widely used than the fact that they started as Proof-of-Work (PoW) or not. This is because these two cryptocurrencies have become staples in the cryptocurrency market, and they have grown to become some of the most recognizable and widely used digital assets. As a result, they have become more popular and widely accepted than other cryptocurrencies that may have started as PoW or other consensus mechanisms. Additionally, the fact that these two cryptocurrencies have been around for longer than other digital assets has likely helped to increase their popularity and usage.