So, can't argue that most acoustic instruments don't translate "realistically" via MIDI and sample libraries. But, some libraries produce better results than others. I think we all are just looking for passable sounds for our instruments.
Whether it be drums (cymbals can be played in an infinite number of ways) but we get a few articulations that we need to make work in a mix or guitar tracks (forget about strumming chords with realistic rhythms and techinique.
So, if you want a realistic bass part, depending on how realistic, I agree you need to record the bass LIVE. But if you just want a passable bass part, some libraries are better than others. Perhaps some day, audio to MIDI translations can advance to the point where cc data is used to translate all the little stuff that makes a real track sound real. I use a MIDI guitar controller and even slides between notes get translated but not translated well (a combination of low velocity passing notes and pitch bend data is what shows up in a MIDI track when sliding between notes) and yes, most MIDI guitar interfaces are really audio to MIDI real time translators).
Jim