Personally I agree, I do not worm my adult dogs unless I see signs or know they have been eating dead rabbits etc! However, most of the people who ask questions on here are 'pet' owners and only want basic advice. As they may be unlikely to recognise the signs of worms, I think it is more helpful to tell them to worm regularly (but not as often as some vets/pharmaceutical companies will tell them).
I think the reason they seem obsessed with flea treatments is that they try so many different cheap ones instead of getting a good one to start with, which is false economy.
I also don't booster my dogs, and I know this has been discussed on here before. I feel in a position to take these decisions for my dogs, but you only have to look at some of the questions to know that many people do not have any knowldge of dog health/physiology whatsoever.