I agree with the price is probably the #1 reason and requisite core muscle fitness second. Most of the posts in the Hybrid forum result in people buying $400-500 hybrids. A few buy hybrids up to $1000, but it's uncommon to see someone spend $2k on a carbon fiber hybrid.

Bike purchases are largely personal preference. As are car purchases.

I encourage people to ride whatever bike they want; it's getting on any bike that is the goal.