One reason I haven’t seen mentioned: it’s hard to get there. The best you get is a two-lane highway (as in one lane for eastbound and one for westbound). Also because you have to go over a mountain range, there’s actually very few highways to even use.

For the Oregon Coast, in that circle you have 4 highways: 6, 18, 26 and 30. If you want to go to, say, Newport. You pretty much go to Lincoln City and then head South.