When BIAB fist came out it was a pretty unique piece of software. I don't think there was any other software on the market where you can enter chords and get a full backing track with a few clicks. The only other thing that could do something similar, to my knowledge, were the home keyboards of the 80s with an "Auto Comp" feature (like old Yamaha PSR keyboards).
Back then BIAB was a great practice tool (and I believe marketed as such) for guitarists mainly but could also be used to quickly sketch an idea out. I don't think anyone used it for any final production. I think that stigma remains today, that BIAB is a practice tool or sketch pad for ideas.
In modern times, where basically anyone with a little bit of interest can have a small project studio in their bedroom running a pro DAW with tons of astonishing plugins, BIAB compares poorly to its competition on several points. The younger crowd puts a lot more weight on applications needing to be streamlined, offer quick and intuitive workflow, have an attractive GUI and play nicely with other studio software and components. I find BIAB lacking in all of the above. Add to that the popularity of products such as those from Toontrack et al. which ticks all of those boxes and BIAB is sadly outplayed.

I am a working musician and composer and run a small project studio. I use BIAB for practice and on occasion to generate piano and bass MIDI for inspiration that I import into my DAW. I don't use realtracks.