What is the reason for storing 30 gallons of gas, oh let me guess inflation?
No. I guess that you live in an urban apartment.
Fairly simple response would be as follows.
This is a survival thread. Many of the people own generators and chainsaws that run on a fuel mixture of gasoline. When the utilities like electricity are down for a home, they are also going to be down at the local filling station.
Here is an excerpt for a Consumer Reports article of 2014:
Gasoline. During a major storm, you might not be able to get on the road to fill up gas cans, and sometimes stations themselves lose power and can’t pump. So keep enough gas on hand to buy you some time, even if you can’t store the 12 to 20 gallons you’d need for 24 hours of straight running. So, 30 gallons doesn't go far, does it??
Do you have a chainsaw, a lawn mower or a generator? Probably not because you ask why 30 gallons.
I am urban and the most I can store is about 20-25 gallons. My car holds about 15 gallons. I once represented a refinery. There is 4x the storage spaces in cars and trucks in the Los Angeles basin than there is storage space in all the refineries and gasoline stations here. MOST PEOPLE DRIVE AROUND ON EMPTY. Do you? If yes, then you are normal. When an emergency comes up, the gasoline disappears and the politicians start quacking about conspiracies to withhold gasoline from the market.
The questioner also does not live in hurricane alley. Hurricane approaches. Everyone hits the highway out of town and bingo, the gasoline supply is exhausted.