The geometry of the proposed lift makes a lot of difference with the front loader too. Mine won't lift the 430 lb weight box on the end of my 8 foot boom pole when it is straight out and halfway up, but will do it if I lower it almost to the ground and angle the boom pole upward.
To answer the original post question, I think the main use for the boom pole is to lift things when you need to keep them farther away from the tractor, like lifting a rear blade into a trailer or something. If you can lift it farther out, it keeps it from smashing the front of your tractor.