In the pure sense, ftp is not a true research tool. Rather, it is a tool for the transfer of data. One could use it as a quasi-research tool by traversing the directory structure of an arbitrary site, but the payback on this sourt of endeavor would certainly not be very high. Instead, ftp has become an ancillary function to other internet tools, notably archie and the world wide web. In addition to these common uses, it is common practice for posters of Usenet news to include an ftp address of a referenced file. The reasoning behind this is simple: rather than send a file out to every machine that stores news, a reference is sent so that people that desire the file can easily access it.
Obviously, ftp is still a very useful tool. It allows users to quickly and easily transfer files, especially when set up in a hypertext (ie. World wide web) environment.