Who is Mr. and Mrs. Sam Malloy from Cannery Row and what is their importance?

Mr. and Mrs. Sam Malloy are a man and wife who become squatters in the Hediondo Cannery's discarded boiler in 1935 and subsequently rent out large pipes as bedrooms to cannery workers. Mrs. Malloy is given to emotional weeping and desires such creature comforts as curtains, even though the boiler lacks windows.