my guesses:
1. people are lazy, its easy to run a hose and install a few clamps
2. people dont have the skills to work with hard line
3. I will fall back to number 1 which eliminates number 2

1941 Taylorcraft
1968 Charger
1994 Wrangler
1998 Wrangler
2008 Kia Rio
2017 Jetta

I didn't do 4 years and 9 months of Graduate School to be called Mister!