You (or your parents) had to pay for your racquets, and your supply was likely limited.
Kyrgios gets paid to use his racquets, and has an unlimited supply of them.
That's a huge difference in perspective on an inanimate object.
Also, certain personalities need to release the frustration - and the racquet is the most convenient object with which to do that (especially when you have a free, unlimited supply of them). Using the racquet to release the frustration is practical in that it's already in your hands... it is also generally safe (much safer than punching something)...
So, really, I completely understand Kyrgios (and any other pro player) smashing their racquets. It provides a tremendous and very efficient release of frustration, and they have a free, unlimited supply.