Chances are what you noticed first in this photo are the scarves the women are both wearing across their face. You'll see this on about 99% of Vietnam's women who ride motorcycles and/or bicycles because they wish to protect their face from the grit and dirt blown up from all the roadways they ride on. Some scarves are of gorgeous silk and tied fashionably, others are of screaming colors and fastened by loops over the ears, and some are pinned - you'll note many different types, all of which can be pulled down easily to allow the wearers immediate access to easier eating and talking.
This particular spot serves as the central transportation hub for the port area of Nha Trang. It is jam full of taxies, buses, ferry boats, fishing boats, bicyclists, street vendors, and even visiting backpackers awaiting trips out to the various nearby islands.
Vietnam is said to be the third largest rice exporter in the world and much of it goes out of this very port of Nha Trang. It's highly likely that most of the rice itself comes from rice paddies throughout this Nha Trang area and the farmers here are highly dependent on motorcycles, motorbikes and bicycles for their daily transportation to and from those rice paddies.