I think the difficulty is the installation process. I wouldn't be surprised to find out that the challenge of getting that much run to convenient places isn't always that easy and, combined with the regulatory burdens likely involved in something providing that much power is scaring away potential installations.

You have to think a lot of the low hanging fruit locations are taken by now and, even if it's profitable, it doesn't make any profit while you're building it and I've seen a "coming soon" sign on top of what looked like a finished installation for more than a year at a mall near me.