GTA V: The killing spree deterrent?

I finished up Grand Theft Auto V around a week ago - it was a pretty great experience, with pockets of dullness here and there. This week, however, I realized that I didn't once go on a killing spree during my 30+ hour playthrough.

Anyone who knows the GTA series will testify that going on killing sprees is sort of the secondary objective of a GTA game (or perhaps even the primary objective, depending on how you like to play). So for me to play through the entirety of a GTA title and not even consider aiming for a five-star wanted rating is rather odd.

So what exactly was the reason for this? Is GTA V's story or city laid out in such a way that I didn't feel the need to go crazy? Is the story just so good that I didn't want to shift away from it? Or perhaps there's just such an overwhelming amount of content to sift through, that going all sandbox-like with my gun-play seemed out of place?

I took my musings to Twitter to see if other people had found the same as me. If you have any thoughts on the topic, bang them into the comments!