If we want to tax "luxury" expenses, we have excise taxes for that.
Right, but consumption for a business is fundamentally different than a person consuming. When you eat lobster (vs eating ground beef), any extra benefit goes down the toilet, so to speak. Whereas for a business, it's presumably to further the enterprise. Maybe getting a purer reagent will make the product better and drive more sales. After all, a business itself can't have any needs or wants. In any case a business can't have wants to get the $300 reagent just because, unlike a person. The employees can get benefits, but there are strict policies set by the IRS on what you can count as a business expense, specifically to prevent you from putting lobsters as a business expense.
Moreover such favorable tax treatment isn't restricted to businesses only. It's available to anyone that conducts business. If you're self employed you can deduct the cost of your F-150 truck, if it's used as part of your job.