Yeah, but it's Jane Street. They've got the money and talent to do it right and they've got a very strong dev culture that esteems correctness.

And they're in a market where a tiny competitive edge can reap large rewards.

They're rather the exception that proves the rule.

I'm sure all their competitors do the same for the same reasons. But for companies that view software primarily as a cost centre, I can see it going horribly wrong.