Try stuffing a baby quilt through the arm of a regular 6" harp sewing machine. Then try it on a 9", an 11" and bigger. Imagine trying to stuff a queen size through that 6". They might not make you a better quilter but they definitely make quilting easier so you spend more time doing it and you get better faster than you would have. And if you get one that has a stitch length regulator, you're able to slide up the learning curve faster.
I even found paper piecing is easier with a longer throat machine because your foundations don't smack into the neck of the machine as often.