The point is, trees should have substantial junk in the trunk in relation to their overall bulk and height. Branches should be smaller than the trunk at the point they connect, and there are certain ratios that would be perfect for each tree.
When trees come home to live with you from the nursery, they're too skinny. The growers encourage this overly-lanky development so they can get as much height as possible quickly, like the tree is going out for the NBA. Trees look their best when they get some girth, have some permanence, can withstand a strong wind, have bark that's as much a feature as the leaves or flowers, and actually look....like a tree.
This is one thing that's really important for most bonsai. They actually have the proportions of mature trees, even though they're only 18 inches tall, give or take. I'm told that the ultimate goal of girth for a bonsai is an inch of trunk diameter for each 6 or 7 inches in height. I would say that for most yard trees, one foot of trunk base diameter for every 10 to 20 feet in height is good. Once trees get to be 80 or 100 years old, the diameter ratio is getting up there and looking like a tree really wants to look.
Pay attention to girth and you'll be much more impressed. Size matters. Do what you can to fatten up your trees. I know how to do this. I'm good at fattening myself up too.