For retailers (companies that accept payments) it's easier, faster, cheaper and safer ( zero risk of theft by staff or robbery). For regular people that pay it's easier, faster, more linear ( if you have to spend X now, you don't have to have withdrawn it from an ATM or bank before).
The only downsides are underbanked people and companies, which is an issue in itself and needs to be fixed regardless of cash availability (I'm talking in general, but even more so for developing countries and the US(wasn't it in the news recently that the US Postal Service is going to be cashing checks at some ridiculously expensive rate? Way to get in to the 19th century!)), and of course privacy, for which regulation is needed ( who has access to your payment/transaction data and in what cases) and it's solved for 90% of cases.