L2s Become More Valuable than L1s?

In theory, L2 blockchains will become more valuable than L1s. If one of the primary reasons for holding an L1 token is for its use within the ecosystem, but an existing L2 is faster and cheaper, why hold L1 other than paying for fees when using the L2?

For a concrete example, if I'm buying NFTs on Opensea and I use Polygon, I'd rather hold more Matic than ETH because all I need ETH for is fees, but Matic is what I use to interact with the Dapp and purchase goods/services.

I understand this is specific to ETH, but I'm curious about your thoughts.

And in this scenario assume, that it's agreed upon that BTC is the store of value (property) of the crypto-verse, so we don't use ETH as a store of value.