Every professional photographer I ever knew or heard about takes as many photos of a given subject he can while the conditions are optimal, knowing that he will sift through them selecting the one that captured the moment the best and discard or archive the rest.

That's my approach which lends itself more affordably to the digital medium.

You have nailed it with that statement. This is the difference between Photography (note the capital P) and "happy snaps".

If one is taking happy snaps, one is satisfied with a single exposure of a given subject. The purpose of the picture is to capture a moment, to record an event. But when a Photographer is practicing his Art, limiting the work to a single exposure would be foolish.

Good Photography isn't all trial-and-error. It does require skill, you still need to frame the subject, control the exposure, and know how to operate the equipment. But the real art in Photography comes in choosing the best exposures out of a selection of many.

It's just like recording music. You don't think those songs on the radio were laid down in one take? No, every phrase was recorded over and over again until they got the take they wanted. Well, OK, there are exceptions, like the Beatles' recording of "Twist and Shout"...

The beauty of digital photography (and digital music recording for that matter) is that the media is random-access and rewritable, so you can blow through even more exposures and more takes than you could back in the days when you were wasting film and tape.