1. Because first-party support IS the reason to get a piece of Nintendo hardware. Even Nintendo platforms with either tons of quality third-party games, or just a sheer quantity of them, still are true to this.
2. Because at this point people accept it. They know very few first-party Switch games will go on sale or get a permanent price cut. They wanna play the game and don't want to wait years to get it cheaper. The evergreen nature keeps the price up.
Lifetime Sales Predictions
Switch: 151 million (was 73, then 96, then 113 million, then 125 million, then 144 million)
PS5: 115 million (was 105 million) Xbox Series S/X: 57 million (was 60 million, then 67 million)
PS4: 120 mil (was 100 then 130 million, then 122 million) Xbox One: 51 mil (was 50 then 55 mil)
3DS: 75.5 mil (was 73, then 77 million)
"Let go your earthly tether, enter the void, empty and become wind." - Guru Laghima