The term "hobo" is a reference to "hoe boy." These were what we would now call "migrant workers," who made their living travelling with hoes on their shoulders, seeking work from local farms. The opening of the country by railroads around the time of the Civil War helped make this a viable way of life.
Given that these men needed to carry hoes, anyway, attaching their goods to the end of these hoes made sense. The hoe was a "lever," which could lessen the burden of the weight being carried on it. See Archimedes Law. It was also less clumsy than carrying goods with two hands.
There was little (but greater than zero) danger of their goods being stolen because these were just their personal effects, typically of the poorest quality. Because they were "poor," (and seen as such), they were the "last" people anyone would want to steal from.