But we're not discussing on the scale of minutes, we're discussing sub-second intervals that aren't even perceptible to humans.

This whole argument seems to boil down to "I don't understand why anyone would want to trade more often than X, therefore nobody should". What's the difference between 5 minutes and any other arbitrary time period, other than hand-wavey notions about "perception"?

I'm still not sure what problem removing my ability to cross the spread whenever I like is meant to be solving.

> I'm still not sure what problem removing my ability to cross the spread whenever I like is meant to be solving.

What problem does it solve? Why should we have so many expert programmers and mathematicians spending their time competing in a 0-sum game that could simply run a bit slower and produce the same societal value?

Flip it around, what economic problem does enabling you to trade more often than once per day (say) solve?

Trading more frequently reduces uncertainty (it's harder to predict 24 hours out vs. 1 minute out)and uncertainty equates to risk which means trading only once per day could increase the cost of capital.

You're basically asking "What economic benefit does a free market bring?" at this point.

It's easy to list the benefits of free markets, I don't think it's easy to do the same for sub-second regulated markets vs 1 second regulated markets.