Swiping is not obsolete. I don't know why you're trying to compare a virtual retailer like Amazon to shops that have an actual physical presence. The way they process payments is entirely different.
Not everyone has a smartphone. Why would Starbucks want to deal with accepting payments via mobile-geolocation and plastic for everyone else? It would just confuse the cashier. Swiping is uniform and only takes a few seconds.
Square fills the mobile payments processing niche where you need to be able to accept plastic when you're not in front of a register. Plumbers, repairmen of all sorts, traveling salesmen, people selling items at fairs/festivals, etc. These people aren't currently able to accept credit cards with real-time processing. That's the problem Square solves.
Not everyone has a smartphone. Why would Starbucks want to deal with accepting payments via mobile-geolocation and plastic for everyone else? It would just confuse the cashier. Swiping is uniform and only takes a few seconds.
Square fills the mobile payments processing niche where you need to be able to accept plastic when you're not in front of a register. Plumbers, repairmen of all sorts, traveling salesmen, people selling items at fairs/festivals, etc. These people aren't currently able to accept credit cards with real-time processing. That's the problem Square solves.