I don't think SSAO is really ever selected over more realistic methods for artistic preference. High budget animated films tend to go for ray traced methods even when they have a non-photorealistic style.
For what it's worth, the existing game console hardware at the time was the Xbox 360 and the PlayStation 3, so SSAO really would have been ROI back then.
'just cheap' = 'actually viable at 30-60fps on mid-spec PC/console'
If you have to real-time light everything, then there's not a lot of other viable options to make your scene look a bit more solid and objects look more grounded for the cost of just a couple of milliseconds of GPU time.
SSAO is just cheap.