I believe it's because of the sales process: a salesperson wants to know if they're talking to a person that can make a purchasing decision, and also wants to

I believe it's because of the sales process: a salesperson wants to know if they're talking to a person that can make a purchasing decision, and also wants to give the customer they're dealing with the impression that they're more influential than the actually are. So there's a natural tendency for both sides to overstate their roles. But then once the guys in sales get more impressive sounding title, everybody wants one and thus, title inflation.