JamesNoBrakes

Couple things:

It's a good way to get plowed into by an airplane on final, since your attention is towards the runway and you are likely blocking out a huge portion of the sky with your wing the entire time where you might notice peripheral movement.

Given a little bit of tailwind on base, it's a very easy way to overshoot final, since you're not allowing any "wiggle-room" in there to allow for the wind, this also helps to set you up for an extremely steep base to final turn and the possible "stall-spin" scenario turning final.

The idea that you "have to fly so close that you can glide to the runway" screws up approaches and patterns in other ways. You can relatively easily make it to the runway in most situations by making a direct b-line to the runway, and in many cases on downwind you still got to extend out some so you don't overshoot on final. People tend to forget that you have to "string out" the pattern and the glide-distance. A lot of light airplanes will go ~1.5 miles for 1000', which means you don't have to be flying a .25 mile pattern, in fact those tight patterns will cause endless trouble when you start to get any tailwind and try to adjust. You're setting yourself up for an over-run/loss-of-control/runway departure by coming in completely power off with flaps. It's fun to do sometimes, but making the reason "so I can glide to the runway" isn't a great one IMO.

They have segments of traffic patterns for a reason. Lots of pilots like to ignore these reasons and do their own thing, which hurts safety, but it's a good idea to do it "the right way", then if you get into trouble you can go back and show that you were doing it the right way at least.

Jets traditionally don't fly patterns. They sometimes do circling approaches, which are a bit different, due to the instrument conditions and usual lack of other traffic. Jets usually fly instrument approaches, even in daytime. When they are flying visual approaches, they are often still using some form of guidance. Not always, but it's common and it's another measure of safety for them, because it gives them something else they can check their progress with. There are plenty of jets and turboprops that do fly patterns, and most of the time they do fly square patterns, or come in on base as directed, etc. Often air traffic control will put them on straight in approaches and make everyone else extend or hold, because they move at a much different speed than everything else. It's not real common for jets to be flying at uncontrolled fields or just doing visual approaches and landings. Yes, they do, but not often. If you ever look at how air-traffic control radar-vectors the big aircraft at big airports, they very often do move them around in the "square" pattern, although it's much bigger (doesn't have much to do with this though). So what is safe and normal in a jet isn't the same as in a light airplane flying in a pattern.

I would say the reason a lot of pilots do this in practice is that they don't realize where their aircraft is drifting on the downwind. They don't understand how to maintain a constant ground track. They don't adequately plan for the turn radius of the airplane and the wind effects. They get their attention centered on the runway because it's the "center of attention" (see the airplane that plowed into the truck that was crossing short of final), so they don't realize what's happening in the turns and where the airplane is going. A tell-tale sign is sitting next to a pilot and watching where he looks. If he is spending most of the time looking in a direction other than where he's going (like fixated left, because that's where the runway is), that is generally bad and I'd run away! These all lead up to having to make the "constant turn". These are all errors.