My question here is: why can't a business make an "unnecessary business expense"? Are businesses legally forbidden from doing so? Really? Why? Or does it just

My question here is: why can't a business make an "unnecessary business expense"? Are businesses legally forbidden from doing so? Really? Why? Or does it just mean that the business can't deduct it from its earnings for tax reasons? In that case, why doesn't the business just pay the extra tax? In my eyes, there's nothing wrong with paying tax. I just cannot understand why anyone would make a rule against such a thing. (Note: as you probably already understand, I do not run a business.)