Formula was also invented to make them MONEY first and foremost- people forget it is a business with a HUGE profit scale. Of course they advertise formula use to the ends of the earth, they are growing their business and their profit margin, their top concern isn't the health of your child, its stock holders.
This! Just because it was invented doesn't mean that it's superior to breast milk. Profit-making companies aren't usually thinking about your best interest. That doesn't mean that you should feel guilty if you can't breastfeed; formula is a fine alternative if you can't breastfeed. As Aliss says, it's better than giving them animal milk as people used to do if they didn't have a wet nurse.
If the regulations were changed to allow formula companies to advertise however they wanted, you could be damned sure they'd try to market their product as being just as good or even better than breast milk, and we all know that's just not true. These companies have been sending me tins of formula (which is making me angry as I don't want it in the house and I have NO IDEA how they got my information and figured out that I'm having a baby. I read through their leaflets for a laugh and am quite amazed at how sneaky they're being with their rhetoric. They are certainly not out to help you -- it's entirely about making money.
That being said, if for some reason I cannot breast feed and cannot obtain breast milk from the local breast milk bank, then I will certainly use formula and not feel guilty.