Agreed that stealth is the main factor for anglers and the one most commonly neglected. The other observations all make good sense in my opinion. The point about what others are up to is also well taken. There is not much point in you being stealthy if the bloke on the opposite bank is standing and casting in full view of where you want to fish. One reason I prefer to fish alone actually, I have generally found it impossible to get people to be stealthy enough. They always seem to think I am exaggerating or being "too fussy". If you can get within 20 feet of a wild deer grazing in a field, using whatever cover is available, and assuming that there is cover, then you might have a chance of getting that close to a wild trout as well. Of course that only means you got that close, it doesn't mean you will catch it!

It is also an interesting exercise for people to try. In the majority of cases you will reach a point where the deer "stiffens" and it ceases to feed, shortly after that, if you continue to advance, and sometimes even if you don't, the deer will just run away. The exact same thing happens with wild trout, it's just that most people never notice, because the fish are long gone before they even get within casting range. It is VERY VERY difficult to be stealthy enough to approach a wild creature without it becoming aware of you, in my opinion the most difficult aspect of the whole affair.
TL
MC