LN not having data on-chain imposes severe constraints that make LN inherently more centralized and less secure than zkRollups.
If you're really set on payment/state channel networks like the Lightning Network (Bitcoin), Raiden (Ethereum) or Connext (Ethereum), you can put them, ON A ZK-ROLLUP!
You get a 100X scalability boost, without increasing the block size, which makes payment/state channel opens/closes a couple orders magnitude lower, which massively increases a payment channel user's options and improves the functionality of the payment channel network. ZkRollups also reduce the cost of on-chain payments which lets a user switch to on-chain for an application that the zkRollup-based PCN is ill-suited.
All-in-all, reducing the cost of on-chain transactions, as zkRollups do, have significant advantages, so there is absolutely no reason to not adopt them.
And Liquid is a centralized sidechain dependent for its security on trusted third parties, and completely incomparable to zkRollups, which have 100% of the security of the mainnet and are only reliant on 51% of the hashrate being honest for security.