If you want cheap transactions, for actual cash-like usage rather than a "settlement layer", you need big blocks. It is not rocket science.
For a miner, currently the latter is negligible. Increasing block size implies more storage space needed, which would push amateur miners out, making Bitcoin less decentralized than now[0]. Over time, the storage costs will become massive. This is why block sizes have stayed relatively low.
One reason I'm bearish on Bitcoin is that it's absurd that a one-time fee allows you to essentially have a permanent public billboard. For example, people have posted links to illegal content on the blockchain that is essentially unremovable[1].
for example the uniswap contracts can be deployed on arbitrum. users can then swap coins on the arbitrum blockchain rather than ethereum and therefore save gas costs