There is a lot of resistance to parking reforms. Makes projects more marketable. No administrative apparatus. Carpools require on-going support. Parking is perceived to increase the marketability of projects and is risk-free.
Bankers are also reticent to go below code standards for parking.
Transportation planners often call restrictive parking policies, higher fuel prices, etc. This is actually a misnomer. Place solo-commuting and vanpools on equal footing. One of the saving graces of traffic congestion is that it is self-regulating. This suggests their is a window of acceptable commuting times for most Americans.