I spotted something in the users manual that says VST's can be used on any real track. I am only able to load amplitube, the other's (including sforzamdos) are just ignored when trying to add them. so my question is two fold: Is it possible to add vst's to realtracks but, secondly, is there any good reason why one would want to do that?

One might well want to load effect VSTs, which is what amplitude does, of course.
I doubt there's any point in loading a VST instrument.

VST FX, sure why not.

VST instrument is a different beast. A lot of real tracks have their Midi counterparts that are loaded at the same time. You can chop away RT, leaving just MIDI and re-voice it with VST instrument of your choice. For example, I use several RT's that I like, but I either used them too many times, or simply don't like that particular sound. So, I would get rid of RT and use that midi with other Virtual instrument(s)

also if you use a Direct Input guitar you can any VSTFX to get the sound you like rather than just take what you are given with the FX version.

Will you elaborate on chopping the RT and have the Midi left?

Any RT with an underline will have a MIDI file with it. I work mostly in a DAW so I drag the MIDI to the mid window, go to DAW mode, and move the mid files via the + sign into my DAW. One maybe able to do it in BiaB but I have no experience doing it, thus other will have to help.

Notation that accompanies some of the RealTracks is for educational purposes. If a piano track has notation, it may be the digital equivalent of the audio that the artist recorded. Some instruments, though, lack the nuances that make it realistic, such as dynamics.

Works OK here (image below)
Yes, there is plenty of reason for doing this if your ears know what needs to be done...
like Mario and others I usually move out of BiaB before getting this far along in my usual workflow, but it can be done
/I used a simple, free, yet effective plugin as the example in the image, but I could just as easily have loaded an Ozone, or any other plugin that will run in BiaB