Also I really don't understand why staggered joysticks are the standard.

In case you were actually curious, here is the reverse timeline:

• Staggered joysticks are the standard because Microsoft Xinput is the standard.
• Xinput is the standard because for about a decade, it was the one controller interface that actually worked without issue for a lot of people.
• Microsoft controllers worked for a lot of people on PC because Microsoft controlled the most popular console and the most popular OS. Sony and Nintendo had no interest in supporting their controllers for PC.
• Microsoft maintained a similar controller layout to their original Xbox console.
• The original Xbox controller was designed before the advent of popular dual-stick games (the first of which was the original Halo). At the time, the right control stick was seen as a secondary control for the camera in third person platformers (see also the c-stick on the Gamecube).
• The original Xbox controller design was cribbed from the Dreamcast, which was to-date the nicest and most ergonomic controller. The Xbox design added the second control stick below the buttons.

Also of note:

• The only other dual-stick design at the time was that of the Playstation, on which both control sticks were secondary, an afterthought not even present on the original PS1 controller. Making the left control stick "primary" was progress.
• Nintendo briefly ended up in the same boat as Sony, when they added secondary control sticks to the original SNES design to create the Wii Classic Controller.
• The only controller that tried to make both control sticks primary was the Nintendo Wii U, which unfortunately failed for unrelated reasons. I had one, and the symmetry was glorious, for those few brief years.
• Nintendo relented and went with the staggered design for the release of the Nintendo Switch, on which the asymmetry was necessary in order for both joycons to also be able to function as separate controllers.

staggered joysticks

I find them more comfortable. The left joystick is the primary for movement, and the primary interface should be on top because that's how thumbs work. The right needs to jump from the joystick to the buttons, so having the buttons be to the top and right makes sense (again, where thumbs go).

I have a PS4 controller for my PC because it supports Bluetooth and works OOTB with Linux, but I honestly prefer my old XBox controller. I'm probably going to get a PS5 controller, not because it's more ergonomic (it's not), but because it has gyro aiming. Playstation controllers aren't uncomfortable, they're just not as comfortable as offset joysticks.

Why do none of these have trackpads?

Maybe they're trying to aim for the crowd for whom the Deck is too expensive, and shaving off some of the hardware helps?

I mean, it does sound like a significant drawback, but if you gotta get the cost down, I suppose that's one thing to look at.

That's a valid concern, hopefully Lenovo is smart enough to not insert themselves in the software pipeline between Valve and their customers.

The way it works with handhelds right now (Bazzite instead of vanilla steam OS), there's certain things that have to be enabled to get the hardware side of things working (all the buttons and inputs etc), but it's still really easy to both update and to use and I haven't had any problems with the ROG Ally X or the Lenovo Legion Go running Bazzite. I dual boot windows (and have group policy edited pretty much all of Microsoft's BS tracking and AI to banish it to that shadow realm) for windows only games that I couldn't get to run reliably in proton, but I'm really happy with it and I'd imagine steam OS coming to such handhelds officially would benefit users rather than being a detriment as far as ease of use goes.

A big problem with Android is ARM vendors don't upstream anything in so you need to run very specific kernel and bootloaders just to boot the OS. SteamOS on x86 won't have that problem, regardless of who makes the end device.