Those who crop regularly are probably taking a lot more photos of a bigger variety of subjects.
i.e. the inverse of the quoted statement is: "People who rarely crop are usually concentrating on getting that "one good shot" and miss many opportunities that other photographers are taking advantage of."
B.S. Paying enough attention to what is going on around you so that you can frame the shot reasonably tight does not prevent you from taking advantage of a photographic opportunity. You are more likely to capture something interesting if you are sufficiently in tune with the action to frame a decent capture than if you merely point the camera, machine-gun the motor drive, and hope to crop something interesting out of the resulting mess. I've been known to shoot well in excess of 1,000 frames at a wedding or concert, but most of the time I crop only to change aspect ratio. It is a rare thing for something "interesting" to happen while I'm shooting without getting at least one reasonably good shot of it. If you are paying attention to what's going on around you, most of the time you can anticipate the "decisive moment", and the fraction of a second it takes to tweak the zoom setting and double-check focus does not impede you from nailing the peak of the action, whatever it is.
3 Principles Of Being An Excellent Photographer1. Know your gear intimately, inside and out.
Making the correct adjustment for any given situation should be instinctive. If shooting conditions change, you should know whether changing ISO, aperture, or shutter speed is the best option, and why. You should be familiar enough with your gear to make those changes immediately, so that you aren't missing an opportunity while attempting to figure out how to adjust a setting. The less time you spend futzing with your gear, the more time and attention you can devote to observing what is going on around you and capturing it well.2. Know your subject just as intimately as your gear.
Anticipating action is critical if you expect to photograph it well. Knowing what is going to happen before it happens give you time to prepare yourself and your equipment so that when the time comes, you are already there and all you have to do is press the shutter release. If you're shooting an event, go to the rehearsal if there is one. This will not only give you some excellent opportunities for candid shots, but it will also allow you to test various camera settings and shooting strategies, rehearse the sequence of events so you can find the best shooting location for each part of the ceremony, and iron out any conflicts between what you are doing and the expectations of the client, venue staff, and other participants. Learn as much as you can about the cultural significance of what is going on, (like the significance of changing shoes at a quinceanera); this will help you recognize and anticipate significant moments so you are ready to capture them when they happen. Learn as much as you can about the people around you; the presence of a particular person my be much more meaningful if you know that they are significant to what is going on. For example, if you are shooting a Black History Month event, knowing that that old guy sitting in the back is one of the Tuskeegee Airmen will probably affect how you shoot the event and enhance your client's satisfaction with your work, especially if you're an albino cracker like me.3. Have a backup plan. You'll eventually need it.
All your skill and creativity as a photographer mean exactly dick if something quits working and you have no backup plan. Don't even think about shooting a wedding or similar event where "do-overs" are not an option without one. Having backup equipment is expensive, but the pain in your wallet is much less than the pain you'll experience the first time you have an "oh s**t" moment in the middle of a wedding ceremony and haven't even shot the formals yet. You should be able to take any piece of gear you have, light it on fire, and still successfully complete the job.