Hacking does not always involve technical wizardry with an understanding of networks, vulnerabilities and exploits. The weakest links in the security chain are invariably humans, and humans are much easier to hack than machines. There are various physical hacking techniques. One example is social engineering, where people are fooled into handing over data. Another is dumpster diving, which is going through garbage for finding compromising information.
The easiest physical hacking technique is merely observing a person using technology without them being aware. After the demonetisation of currency notes, there has been an increase in the number of people using digital wallets and banking apps on their phones. If using these applications in public, it is trivial for someone observing over your shoulders to get your data. In buses, trains, malls, theatres, or other crowded areas, it is better to avoid entering login details and passwords entirely.
This method is called Shoulder Surfing. People proficient in technology can track keypresses by just looking at your fingers, even if the details are hidden by asterisks. Even users who are not actively out to exploit accounts may get tempted on learning the login details and passwords of people. The online banking system in India is one of the most secure implementations in the world, but it is still better to be safe than sorry.