I've heard that too, about advertising to make sure a rival doesn't fill up that space instead.

It's also necessary for publicly listed mega-multi-national corporations that answer to share-holders, to not just make profit, but make more profit than last year.
With small businesses, it's great to make more money each year, but as long as you make money, that's still great. But with big business that has shareholders, it's not enough to actually make a profit anymore, because most corporations on the sharemarket will end up with a drop in their share price if they don't earn more than they did last year/quarter, or meet their projected target of increased profit... regardless of how much they actually still made as a profit.

It's often why the workers get screwed when cost-cutting is the last resort to meeting profit targets (after expenses), just to please the share-holders who don't even invest into the business to make it grow (or just for the personal benefit of the the CEO making the cuts, who often has a healthy amount of shares and/or profit bonuses).
Imagine if one of our big four banks or Telstra reported $2 Billion profit for the year. You might think that's a great result, and think that the shareholders will get a healthy dividend... but with each of them racking up $8-10 Billion annually in profit in recent years, a drop to just a quarter of that would send the sharemarket into a nosedive, because of the kneejerk reaction of share traders pulling their money out of the market assuming the worst, when in fact, the business is still very healthy (too healthy with all the fees the banks charge and still want more each year), and that sort of shock to the market would result in a devaluing of the business (and other businesses on the stock exchange), despite it still making a lot of money.
Our society is too addicted to the share market, which is such a fragile element of the financial world... and with most of our super funds heavily invested in share markets, governments will do anything to keep them afloat (which benefits the rich, while the working classes have to pay more in taxes and bank fees to cover bailouts or new financial regulations/requirements - eg. Westpac raising interest rates).
(end of rant)