Why do people create virus ?

I wonder why people waste their brain creating these crazy viruses which just copies itself into several locations making us harder to remove.

There may be several reasons Some would say that viruses would only give decent/advanced and better programmers ideas as to new holes in an OS. Thus snowballing themselves with new viruses to deal with. I think I can write the odd piece of malicious code, but i would never use it on anyone but myself. I do it to prove I’m a reasonable programmer and that i understand what an OS is doing in certain instances. It is a quesiton of morality when a programmer or hacker releases code for the use of destruction and corruption, sadly there are more destructive programmers than non-destructive in the virus industry.... even i believe that the antivirus industry creates virus itself to increase their sales..

You may say that i am being pessimist or psychic but that is not the case...

It is true the virus company creates the virus itself probably to increase the detection rate by it's product as the antivirus is judged by the detection ratio.

I believe most people write virus because they feel that they can.....
yes that's the case no ordinary people can create or write a virus it need a master piece brain.
Then why do they just use their brain in the wrong way.