So if you make $X in profit and then use it to buy a tractor, then (from the government's perspective), you've just swapped $X for an asset worth $X. No change in book value, no reduction in profit, no reduction in tax liability.

You are, however, allowed to treat the tractor as an expense that's distributed over several years of its useful life, which is called "depreciating" it.

So yes, to the extent that your cash is exchanged for assets, that counts as a higher book value and higher tax liability (than if it were a pure expense). I don't know if you'd have to treat a "data purchase" more like a tractor or more like buying electricity (a pure expense) though.

My previous, longer comment on the constrains of the tax code and how it results in needing the concept of depreciation: https://news.ycombinator.com/item?id=15060604#15061439

Similar experience here:

In an earlier career my company reinvested all profits back into growth, only to learn that the taxman didn't care about such silly things. The IRS demanded the tax from the profits that had been reinvested and were no longer available.

Plus they wanted the tax from the profits of the growth that had only happened from reinvesting the earlier profits that they wanted tax from. Their demands were in excess of the actual realized profit that had been made by the company.