Because designers and devs don't want to have to do multiple designs. Everyone's aiming for one design that works for everything. The problem is that such a thing is impossible.

Vollying back your flipness-- This sort of reductive assumption about software design is why companies that need people who aren't developers to actually use their products hire interface designers.

Most employers I've had are all about getting engineers to be everything. Designers, infrastructure, QA, UI/UX, and even product/project managers.. everything.

Sounds like you need new employers. The only people who want that are shortsighted managers who don't care that they know nothing about users' needs, and that's certainly not a universal disposition in the software business.

This has been true of every employer I have ever had. It's true outside of "tech" as well but nearly all of my experience has been as a software engineer.

I've worked in the software business for the better part of 25 years and my experience differs.

People are generationally creatures of habit. Newer generations are entering the workforce for whom their first personal computing device was a touchscreen smartphone. With that context in mind, it's not surprising that a "native" responsive experience to them will be mobile centric rather than desktop centric. The market then evolves to cater to the needs of its largest cohorts.

Yes. To engineers, the interface is something you use to interact with software. To users, the interface is the software. When they buy (with money or creepy analytics for marketers) software, they're buying an interface. As anybody in business knows, you're not in the business you think you're in, you're in the business your customers think you're in, and if they expect software to behave in a way it can't, their competitor is a half-inch down the app store results/google listing/etc.

Controls? Regardless of whether or not you like the changes, device usage changes the way people use other devices. What you deem "correct" is not the objective universal truth you think it is. Not knowing that is why almost all FOSS interfaces are an absolute dumpster fire.