You have a point but there is another side to it that is hard to understand unless you have it but basically the advantage is you can fall ass backwards into watching a ton of really good stuff that you never would have seen or even heard of otherwise, or that you wouldn't have bothered downloading.
TONS of 4K content. You can't get that downloading, and that is a totally valid and worthwhile reason to own it. Certainly the best "objective" reason to have it. If you have a 4K TV and are only watching stuff you download, you may as well not even own the TV in the firstplace.
Plus there is the fun of "channel/show surfing" but that's really just secondary.
AND lastly you can share the account with 2 or 3 other people. I do and pay like $4 US a month. Even if I watch like 2 or 3 hours a month its already basically been worth not having to hastle with downloading, hooking up my PC to my TV, and transferring.
Summary reasons to own it: convenience and quality (both picture and programming).
Plus its nice to pay people who make quality things, if that floats yer boat at all