Mom and pop restaurants, ha ha ha.
Hours are long and profit is low. At closing time the last thing that they want to do is scrub down the kitchen. I've done plenty of repairs in the mom and pop restaurant kitchen and they're not any cleaner than any other.
For repairs they always want you there long before opening or after closing. 3am and 9pm rates are not cheap. Especially since most of the time it starts with filling a sink with half a bottle of dawn and hot water to soak the cook stove, fryer and other stuff parts.
"What are you doing that for?" Ummm, they're clogged with grease because they haven't been cleaned in God knows how long.