Sometimes it's because the product is on the way to failure in the market. It might be a great product, but that doesn't mean it'll ever be profitable.

The acquirer may love the technology and use it internally, but it's expensive to keep it in a public marketplace. It requires support staff, marketing, sales, etc.

There are also acquisitions that are purely about customers, so the startup's product is shut down or rolled into the acquirer's existing products.

So there are a lot of good reasons you'd want to company other than its product, but we can't always tell which reason it is right away.

It's a question of whether the acquirer and/or the acquiree have a good faith social contract with the early adopters who take the risk and believe in them.

There is no transfer pricing mechanism for programmers like there is for footballers. Worse, programmers are often loyal to a particular technology or concept. So in order to extract the valuable staff from a company it's necessary to destroy that thing so the staff can be reallocated profitably.

"Technology" is rarely re-used per se.

"So in order to extract the valuable staff from a company it's necessary to destroy that thing so the staff can be reallocated profitably."

I wonder how often this actually works. In most cases where I've seen this (or heard of it happening first hand from people I know) the vast majority of the people you'd want to keep were out the door of the new place pretty close to as soon as possible (meaning, as soon as the contracts allow, or the golden handcuffs are mostly off, or whatever is relevant to the specific situation).

On the inside there tends to be a pretty predictable path: New management tells everyone nothing will change materially, everything inevitably changes very quickly, people get disgruntled and take off for other opportunities (at a quickly accelerating pace as the old guard sees all their former colleagues from the old place leaving the new).

It's Apple. They don't like having lots of public projects, especially ones tangential to their mission, they probably want to weld it firmly to their in-house usage and have it as a competitive advantage which nobody else can buy.