Several reasons...some of which you pointed out...
Bought my first new SLR (35mm film) a little more than 7 years ago, just before the birth of my first daughter. It was a Pentax ZX-30. Very pleased with it - it let me down once while it was still under warranty, but was fine after it was repaired.
The quality was very good - very rugged - could take a beating, and still produce great shots (minus the operator error).
So, the primary reason was the brand had treated me well...I tend to be loyal when I find a good performing brand. Other reasons:
1. Ability to use older Pentax lenses. I only had 1, but $150 is $150...if you can spare $150, I'll gladly take it
2. I like the ability to use AA batteries if needed
3. I like having a brand that not too many other people have
4. I don't think you can beat the combination of price and performance...
Overall, still thrilled with the brand. Unless something crazy happens, whenever I upgrade, it will be to another Pentax.