It's a career devoted to helping a very large enterprise with diverse interests comply with a very complicated, fact-intensive, and generally multinational set of regulations in the same manner as every tax professional since Learned Hand: diligently paying the lowest amount consistent with the law.

Substantially every business owner you know -- the ones with top line revenues of $100k, $1 million, $10 million, and $100 million -- employ 0.05 to 100+ full-time accountant equivalents for the same purpose.

I am on uncomfortably good terms with my friendly local tax office and they're all but begging me "Mr. McKenzie, it will be easier for all of us if you just get a pro to do it for you this time." (Tax agencies essentially delegate surveillance duties to CPAs; a Japanese CPA signing off on my return means the Meguro tax office doesn't have to trouble their heads about how Japanese tax law interacts with an American LLC owned by a Japan-resident American covered by a really complicated treaty.)