Does the S in Galaxy S really mean sport? I don't think it really does. I always thought it meant Samsung. Which is why they made a Galaxy S active. It wouldn't really make much sense to have an active if it was already a sport model.
I would bet dollars to donuts the Note 5 will be water resistant. They didn't decide "we don't want the phone of "professionals" to be prone to water damage" and it certainly wasn't a technological roadblock that prevented it either.
It was probably a matter of time. They wanted the Note 4 released in October, and they didn't have time to get a water resistant version out by then. Maybe they had issues getting the metal to seal properly, as previous posters speculated, so they went with the water vulnerable version and they'll get the water resistance perfected by next year.
Or maybe it was the cost. Maybe they didn't want to spend the extra money to get it right, and they'll revisit that decision at a later date.
I can guarantee you it's not because they decided "it's for professionals, and professionals hate water so they'll never be around it and would be upset if their phone was water resistant."
There is no law that says a phone can't both be for professionals, and also be water resistant. And there is no law that says since I plan on using my phone in a professional environment, I have to hate it if it's water resistant.
I'm a professional, and I take my Note 3 camping, hiking, hunting, boating, riding, etc, all the time. I also take it to work every day.