Excellent question. Wireshark is great if you want to put together streams and view data. But, there's more to Wireshark than that. I don't want to discount that at all. It's an excellent tool, one that I use all the time. Ettercap comes in when you want to do more than view the data. One example where Ettercap would be more useful than Wireshark is when you want to perform injection based on some condition. With this same basic code, we can see the request to the page in the authenticated area of a site. Then, when we see the response, we can inject a BeEF hook when we know they are authenticated. Also, when we come across custom protocols, making a basic parser in Lua is easier than writing one in C for many people. If we want to be able to both view and manipulate one of these protocols-- such as one for a custom piece of hardware-- this is where we hope this effort will be useful.

Which script are you trying to find that it's showing isn't there? You can get to the git rep by going to https://github.com/SpiderLabs/Nmap-Tools and then copying and pasting the github URL. If you are not able to get the binary, you can get it by going directly to http://wkhtmltopdf.googlecode.com and downloading it from the links on the left. I've had a few people test it out, and show that it is working, however some sites it appears that wkhtmltoimage has problems with. It's not really a NSE script bug, but more a problem with the wkhtmltoimage binary as it's erroring out. I'll do some more testing and see if I can find a workaround. Thanks for the feedback.