How often does that mix of being mad and then getting it happen? That story from @noah730 about the sewer line is the perfect example. You feel like an idiot for missing it, but also weirdly smarter for finally seeing it. The slowness of drawing by hand just makes your brain check things in a way clicking around never does. It's like your eyes finally work right.
I redid a site plan last year and had the sewer line crossing through a building on the digital version. Totally missed it because all the layers just looked like colorful lines. Drawing it by hand with a ruler, I got to that spot and just stared at my own stupidity for a solid minute. Felt like a total genius who somehow also can't tie his own shoes. It really does force your brain to engage in a different way.
Digital tools don't make you dumb, they just let your brain skip the boring checks sometimes. Drawing by hand forces you to see each piece as a real thing you're placing. That physical step totally changes how you pay attention.