Welcome to our World! In Honolulu I was lucky last year and only waited 30 minutes, people who were rude to the employees were still sitting there when I left. In Savannah, GA I waited two hours for a car, they had them but didn't have enough people to clean them and too many returns at the same time to manage them well, people finally asked if they could just have dirty cars. In UP Michigan I arrived late at night to find no car, they had two for my family, and the other 9 people from the flight were on their own, no Uber, no Lyft, and a two taxi town. I was able to get my rental two days later though, but only because I showed up at the counter prior to that nights flight arriving. In Orlando, I had an hour wait on one of my trips. In Nashville they had cars but they were delayed, I had to wait about 45 minutes, only because I opted to get an SUV (what I rented) instead of the sedans they kept pulling up with, ended up with a four door Jeep Wrangler Limited. One of the worst experiences was my return to LaGuardia after picking up my rental in Philadelphia, the rental signs for my terminal were all gone due to construction, I had to stop at another rental agency to ask them where my return location was. Good thing I left early that morning!
It sucks that you have no way of knowing if the location you are coming to is going to have cars, or if there is some other delaying issue.