This guy could have had no experience in transacting his eth before. For a normal transaction to be carried out in ethereum blockchain the total amount of gas will cost around 21000. While creating a smart contract more gas volume will be required. For instance while creating smart contract for handling Omise go costed around 1197000 gas. Indeed a huge volume which means more complex a transaction is, the more gas we need to use up for transacting.

A transaction could fail when Transaction gas volume exceeds the block gas limit. But in this case it was a complex transaction which required huge gas and that 21000 gas was not sufficient for the transaction to complete. He should have used 20gwei as price per gas and should have used very high gas volume which could have made the transaction pass.

You may not end up in such a situation as high gas volume are very rare and if you are doing a normal transaction just use 21000 gas and 20gwei gas price for it to conform. The base theory of ethereum transaction is similar to a taxi ride you are going mate. If you need to travel longer distances use higher fuel how complex the route might be. Our routes are simple mate which require 21000 gas so don't worry.
Hope this answer helps