They just might be charging too much, in my opinion, anyway.
Here in San Antonio, there's an commercial kitchen rental company that charges about $30/hr (if you purchase minimum 10-hour block, during peak hours). That's 300 buck for just 10 hours. Prep alone takes more than 10 hours in about 3 days with the limited menu I have planned. PLUS, when you enter into an agreement for block hours, they require a $500 deposit. Even thought the deposit is refundable, It's going to cost me $800 just for the first 10 hours of use of that kitchen. I need to mention that fridge and freezer space is available, as well.
I don't know what the pricing schemes are like elsewhere, but that's steep for a startup in my opinion.
Another factor may be that because of prices like these, food truck owners are finding other kitchen arrangements for better prices. Like renting the kitchen of a small restaurant that's only open until the lunch rush is over. Renting space in the kitchen of a church is another option that was presented to me, as well.
It's understandable for rental kitchens to charge such prices, though. These places are gleaming and sparkling with all the brand-spanking-new stainless steel surfaces and equipment and people on-hand to teach you how to use the stuff if you need that kind of help.