I agree with you that in an ideal world there'd be a way for you to demonstrate your prowess without playing these games. However, in the real world, I want a job, I'm going to play? It's not like I don't solve hard engineering puzzles for fun on my own time anyways. Framing matters a lot!

Here's what I like about interviews:

(1) I get to talk about myself and how great I am without people rolling their eyes at me.

(2) I get to solve a fun puzzle with:

(2)(a) A defined answer.

(2)(b) That I never have to maintain.

(2)(c) With a potential financial windfall at the end.