The world would indeed be a very messy place without garbage trucks. Before organized trash collections, waste was handled by unsophisticated means like burning, feeding it to animals, burying it, or just tossing it over your shoulder.
As times changed, approaches to waste management became more organized and regulated, which gave rise to the garbage collection truck.
The first versions of garbage collection "trucks" were open top horse-drawn trailers that the driver had to hoist a can over his head and dump the contents into. The drawback to this was the refuse was visible and smelly, and a bump in the road could lead to messy, time-consuming spills. Also the driver was prone to fatigue and injury from having to repeatedly lift trash containers up and over his head for dumping.
In the 1920s, the rear-loader refuse truck was developed. It made use of hydraulic arms to grapple a trash container and lift it on top of the truck, dump it out, and put it back on the ground.
Around 1950, the side-loading refuse truck was invented for residential trash collection. The trash was loaded into the side of the truck, either manually or with hydraulic loaders. Large hydraulic blades continuously pack the trash tightly in the back of the cargo area, making room for more trash. The technology that combines automated loading with packing remains in today's garbage trucks.
The automated versions of side loaders require only one operator, compared to traditional rear-loading trucks, which require two to three people. The other advantage to side loaders is the reduction of injuries due to repeated heavy lifting. The top-of-the-line side loader refuse trucks have high-manipulation hydraulic arms that can reach around obstacles, such as a mailbox, to grab trash containers. This keeps the operator from having to move the truck, thereby saving time and fuel.