Why is that some skaters perform their competitive routines with great technique - including pointed toes - while others never seem to "get with the program", as far as pointing their toes are concerned?

Some coaches absolutely insist that their students develop the habit of pointing their toes, and, this really adds to the artistic side of their skating, in my opinion. When a skater lands a jump with a perfectly pointed toe on the extended, free leg - wow.
When a skater performs a camel spin or a layback spin with a well-positioned free leg/pointed toe - wow. Great technique!!

On the other hand, some skaters achieve greatness without pointing their toes. Dorothy Hamill once stated that she never considered herself to be an artistic skater, because, among other things, she never pointed her toes. :D Oh well, that little flaw did not prevent her from winning the Olympic gold medal in 1976!