How do they do it?

Like many I only frequent this site and forum when I have a problem. I'm a "user" I guess.

My computer skills falling somewhere between expert and the ability to totally mess up a compute, I typically resort to my own methods before coming here to take advantage of all this knowledge.

More the point ...recently I accquired the zeroAccess rootkit virus. An interesting variant thereof at least. That would do some tricky things. To make a long story short ....as per past experience.... Mbam, and comboFix took care of the problem ...with only a few necessary hoops to jump through. I was disheartened by the pages of step by step requirements to address the virus so I used these tools and some basic tricks to take care of the problem. I got lucky again.

Anyway ....my question is ......why is it that giant software corporations, experts, engineers, and even anti-virus specialist don't seem to be able to come up with software to do the tasks that this small, efficient programs can do? Why is it that a program like ComboFix seems to be able to do things that no Microsoft program can do? Why is it that a very talented individual can write a program(s) that seem out of the reach of majory software companies?

Kudos and thanks again to the authors of these tools, and to the authors of all the free tools out there, and to places like Major Geeks that support the community. You guys seem to be the front line of defense ......one would think it would be the major software companies ...but no ....it's you guys.
Thanks a million,
JohnnyB