The gas pumps don't work

Why does the credit card machine on the gas pump only work during the day?
At most gas stations in the metro area, the credit card machine only works during the day. After a certain time of night, the pre-pay with your card is removed and everyone that pulls up is required to go inside the gas station to pay the attendant in person. Why would the gas stations turn off the pre-pay machines at the time when both they and their customers are at the most risk for robbery?
I have noticed, with increasing annoyance, that between certain hour’s gas stations stop allowing customers to use the credit card pre-pay that was built into the machine. At these times, all the customers to the gas station must go into the gas station to pay the attendant. In some cases this time of day can be the evening rush hour when the credit card machines mysteriously stop working for all of the stations female customers, yet continue to work as usual for the male customers. However, in most cases, gas stations require all customers to walk into the station and pay the attendant late at night.
This practice would make sense if the gas stations were trying to keep people from stealing the gasoline; however, the pumps that are being used now require the attendant to turn them on for the customer. This means that until you have either paid inside or has your credit card approved you cannot pump gasoline, and therefore cannot steal it either.
What is really strange is that the night time hours when the gas stations are not allowing to credit card machines to work is the time of day when gas stations and their patrons are most susceptible to robbery. It would seem to me that a customer who has to leave their vehicle unattended and walk into the station at night to pay is leaving space not only for someone to steal their car, but also to steal their wallet. The person between their car and the gas station is susceptible to theft from their person mostly because should they be held up in the gas station parking lot the chances of the station attendant are largely non-existent.
Additionally, this is the time when there are fewest people at gas stations. Typically, at night the only people that want to wander around empty gas stations are there to try to steal from the gas station. Asking every customer to walk up into the station means that the doors must be left unlocked at all times, increasing the risk of robbery.
It seems, then, that not allowing customers to use the credit card machines on gas pumps is a practice that should no longer be put in place as the technology increases in favor of the gas stations. Hopefully, this very annoying occurrence will be increasingly rare in major cities, as it already is in smaller ones.