Given that, if min tax rate is 15% and standard corp tax is 20%, the government is happy for you to get to 15% and would like you to get to there with incentives, but not happy for you to get any lower however you do it. The incentives are generally not powerful enough to get you there anyway
https://smartasset.com/taxes/tax-loopholes
"The basic definition of a tax loophole is a provision in the tax code that allows taxpayers to reduce their tax liability."
And corporations readily exploit loopholes (or incentives if you prefer) to dramatically reduce their tax burden below 15%. See, eg, here:
https://itep.org/amazon-has-record-breaking-profits-in-2020-...
Amazon has enjoyed an effective tax rate of 4.7% over the last 10 years by using tax breaks, tax credits, and depreciation, that have nothing to do with offshoring cash.
This isn't to say that I don't want businesses taxed, but if a business had 10B in profits, but deducts 5B for capital improvements, then the 5B in remainder can be taxed at 15%