This article[1] says that in some states it's included in what you have to pay property tax on. That seems like it would push businesses to keep less than would otherwise be optimal.

[1] https://www.boxstorm.com/articles/inventory-tax-explained-fo...

Money used to purchase inventory is also usually taxed as profit, which is a further disincentive.

Yes, and no. Profit is profit and is taxed. After making a profit companies have the option of what to do with their profit.

They can dividend it, use it as capital, or use it to increase working capital (like stock.) Some tax environments tax dividends further, thus making it attractive (or cheaper, depending on you pov) to reinvest the profit in the business.

Of course working capital (stock on hand) can also be increased by other means - for example a loan or a capital injection.

Lastly, raw stock (pile of chips) is easy to value for stock-taking purposes (usually cost basis.) partially, or in some cases completely, finished goods is trickier. They could be valued at cost, at zero (a half finished controller is worth, what?)

Generally companies keep as much as they need, ideally no more. But the right number can be a moving target. We've been erring on the high side for a while now.

It’s not taxed as profit. It’s just a cash (non-expensed) outflow. That’s just a fundamental feature of how modern accounting works.

Companies should not spend billions on stock buybacks instead of keeping their factories in running order but the recent baby food issues in the US show that isn't always the case.

It's not one or the other, they can do both. You think that a company would rather do a stock buyback and NOT keep their factories in running order so their stock will tank right after they buy back their stock at a higher price?

Depends on the vesting schedule of the people doing the buybacks.