To flash the hardware with software at the factory and repair depot. The main power connect to the device is a barrel jack, which is cheap, durable and boasts high energy capacity. The downside, however, is that data cannot be transmitted to flash the device through a barrel jack. A micro-USB alone cannot deliver sufficient energy to power the heavy duty speakers. A USB-C could potentially transmit both sufficient power and data; however, USB-C adds more cost to the BOM over the combination of barrel/USB-Micro (and wifi module). To optimize the user experience (and for environmental reasons), Google is moving to an energy-efficient USB-C universal port on all their devices, however, so future re-freshes are unlikely to have this.