Not just about PoS device. During early credit/debit card days, lot of stores would pass on merchandise fees directly to customers, giving discount in case of cash transactions, some stores still charge extra. This is not allowed in west as credit cards require same price as cash transactions, and most users perceive credit card rewards as something positive as one would lose out on this rewards when using cash. In India perception is that one would be making loss* if using credit cards. UPI with no fees as of now, is perceived as equal to cash by most people not dealing with black money.