What are lawn vacuums used for, and do I need one?

I saw something very interesting that looked like a typical lawn mower, but the part the engine sits on is raised and the wheels are taller and closer together.  I sometimes do lawn mow with a lot of rubbish in the front and backyards and was wondering if this machine would be a good investment. 

I have coconut shells, aluminum cans and general rubbish that I just throw out the kitchen window because I'm too lazy to empty out the kitchen bin..