It's not clear to me that the financial system as an enabler of liquidity/commerce/trades/etc. would be significantly worse if the granularity were slightly reduced, though. Say, run exchanges in a discrete-time world of 100ms timesteps. Are there real-world use cases where this would make the finance system unable to facilitate the economy?

If there are ways to make profit by trading at sub-100ms resolution, but a 1ms-resolution exchange is not any better at facilitating the outside-finance economy than a 100ms-resolution one would be, then it seems like HFT is solving problems of the exchange's own creation. It could even genuinely be solving those problems, but if they're problems that only arise in the context of extremely-high-granularity exchanges, and there is no practical benefit to such high time resolution, then why not just axe the problems?