Kleinstein, you are right, but you are also speaking from a professional point of view. For a hobbyist, building equipment is a learning experience, also an imperative. You build a limited LM317/LM337 linear supply, learning a lot (morale boost), and move on to use it for other experiments. You become aware of its limitations, and learn more. Then you decide to build a better supply, and you're ready for it. My first homebrew power supply was a bipolar 317/337 inspired by the Elliot sound page, mains kit ripped from a IBM computer, huge capacitance multiplier included, with a voltage meter taken from a ultracheap chinese analog multimeter. I still use it a lot (I'm not a pro, obviously), though I've upgraded to a 723 design. Using this first supply, I soon learned to detect a short because the transformer started humming and the voltage dropped almost to zero (clack!, the cheap analog meter dropped and bounced). As long as you don't bypass the 317 with transistors, the crude protection is good enough for a beginner.