The -- and really, the ONLY -- thing going for VB6 is the ease of integrating rudimentary visual controls to create a GUI with minimal effort. You can get a pretty sophisticated GUI (I'm embarrassed to say that I have maxed out the number of available widgets -- text boxes, labels, drop-down selection lists, etc -- on more than one application) in nearly no time. The code that gets generated is incredibly slow, but if you're super-duper careful, you can squeeze reasonable performance out of the compiler. It never gets above reasonable, though.
I've tried writing a GUI in C, and it was an awful experience. Same for MATLAB. If you allows me to call web pages a GUI, then same for PHP / Perl, and it was only slightly less painful.
I wrote a very simple GUI in Visual Studio 2010 C, and it was ... OK. Wouldn't want to make a really complex one, though.
So, in the end, there is a reason to use VB6, sort-of. Kinda. Maybe. If it ran on Win7, there'd be a stronger case for using it.