A big company wants to buy a little company. The big company is publicly traded. It wants to use some combination of cash and stock to buy the little company. How do negotiations even begin? Like...where would they start?
Well, how about the clever starting place of just shrugging and suggesting "Eh. Half cash, half stock? That work?"
Well, that would be a problem for the investment bankers, who then don't get to make the deal exceedingly complicated and thus amortize their MBAs. But half stock is the kissin' cousin to half cash in an acquisition as the currency of choice.