Why is cubase your daw of choice.
Far too many reasons to list…but heres a SMALL sample:
SX 2 was the first REAL DAW I was introduced to (“Fruity Loops”, now FL Studio, lead me up to it though)
FULLY integrates with my Motif XS!..!!
Steinberg created VST technology 
Always loved the workflow
The Editors are second to NONE
The power/tools it wields
The customization
Love that its not the “studio standard” as well! 
etc
etc
Why WOULDNT you choose Cubase 
(especially at its current version!..!..!)
NO BRAINER
Because I had Cubase on an Atari ST (in turn because I had Pro-24 on an Atari ST) and I (a) don’t want the trouble of learning anything very different and (b) do always want a good chance of being able to open old files in my latest DAW.
Because my keyboard teacher introduced me to it and it works for what I do. Can’t be bothered to look elsewhere when things are smooth 
PRO 24!!! That’s what I started on! I still have a couple dozen floppies with old song files. Are you saying Cubase Artist 6.5 will load them in???
No, I’m not, unfortunately.
I can’t remember whether any PC version of Cubase would load Pro-24 files, though I think not. But I was able to load Pro-24 files into Atari Cubase and save them from there. Later, I was able to get Atari Cubase ARR files into PC versions (IIRC, SX3 is the last version that would do that). I can think of (at least) one piece, now saved in a relatively recent Cubase format, that originated in Pro-24.
I just had a quick look in Cubase VST v5 (predecessor of the SX versions) and it looks like that wouldn’t import Pro-24 files. Unless an earlier VST version would import them [I think I still have v3 on an old PC but it’s not easy to get it going to find out] perhaps the only way you could get your Pro-24 music into modern Cubase would be via Atari Cubase? Not impossible, but not much fun.