>The stock market is a zero-sum game. Every single penny taken out was a penny put in. Money going in is people's pensions, largely.

Ah, so you lack a basic understanding of how the stock market works, but think you're qualified to make very strong statements about it.

Trades batched by second would provide as much liquidity as anybody could use, without the yachts.

You can start a new exchange that does this batching.

Btw, you need to be careful, because people might still race to be the last (or first) to contribute to a batch.

They'd race to be the first, if tied prices within a batch are resolved in favour of the earlier bird. Otherwise, they would race to be the last, so they have the most information available when deciding on their price (and so that they can change their mind until the last nano-second.)

And if ties within that second were resolved randomly, what perverse optimizing would you predict?

Well traders do provide liquidity which saves pensioners enormous sums compared to selling retirement assets at will into illiquid markets

Granted traders can play other games, but their primary benefit to others is significant