Why? One of the production goals of software is to minimize inventory time. Software that is written and not shipped incurs capex without revenue, unlike tech debt - I can put an explicit number on this cost. Similarly, software that goes unshipped also does not get customer feedback. It may be worthless.

There’s a balance here - but it’s not at all obvious what the balance should be in every business.

You're right, every business is different, and that goes for software businesses, too. I'm thinking that Twitter's central position re the dissemination of information, and its international scope make it a fairly high security operation, in this day and age, whether it wants to be or not.