That was one of the first things I noticed about the Model 3's dash. By not having an instrument cluster in front of the driver, the dash is cut down significantly over a regular car, all the way across. I'm not exactly sure, but I think those contours extend out across the nose of the car. That adds up to a considerable weight savings, probably a couple of hundred pounds overall.
They end up needing less steel for the dash/firewall (that portion of the car is steel in the Model S/X), less aluminum in the nose, as well as simplified wiring harnesses in the dash. I've read the wiring harnesses in the Model S and X are one of the biggest pains with manufacturing. The cars have wiring going everywhere.
Everything in the car is a cost trade-off. They probably looked at manually cranked windows, but power windows have become so ubiquitous the manual mechanism might cost more than the power mechanism these days. Or the cost difference (with manufacturing costs) was negligible.
Eliminating the driver's instruments and putting everything on the center screen allows Tesla to cut down the dash more than just about any car on the market. They will probably pitch it as a feature (better forward visibility). This probably will be the wave of the future when cars become 100% automated. There will be no actual driver. One person will punch in the destination and the vehicle will do the rest. There will be no manual override. But that is sometime in the future. It's going to be several years until the software for that sort of thing is ready and another number of years until regulations catch up.