Because pretty much every picture you see of the guy are snaps from a professional photo shoot where he intentionally peaked, tanned, manipulated water/carbs/sodium, and pumped up immediately before the pic was snapped.
This is a quick snapshot from one of his training vids last year:
Not the best idea at all, but it's more likely
a better reference to his regular walk-around condition. No tan, no flattering angles or flexing, but he is mid-workout, so it's still
not "standard" shape and there's very likely some pumped up muscles.
^ That condition is totally achievable for day-to-day maintenance, without a doubt. There are guys on this site that have done or are doing it. Drugs can help, but it still takes that whole "build a base over a decade or three, train with a good program, and be hyper-vigilant about every calorie you take in."
Since all you care about are the drugs, read this, where a Mr. Olympia-level bodybuilder outlines his AAS use.