Here's what the appeal is for me:
1) A device I can use at the bed/crapper comfortably -- to read, check email, browse, etc.
2) I'm a hobby artist (from the Amiga days) and I love the digital painting apps and Apple pencil.
3) It's my main reading device. I have tons of physical books (several thousands), but its now cheaper and more convenient to read PDFs, ePub, etc books. I use Apple's Books and the iOS Kindle app.
4) Photography. It's great for sharing with friends nearby, casual edits on the road, having your portfolio in an easy to show, glorious screen.
5) Music apps. If somebody does guitar, piano, or electronic music, there are tons of apps, from amp modellers to complete DAWs, and tons of "VSTs" (AUs in our case).
6) Great for note-taking, drawing diagrams and so on.
7) Handy to watch a video in something less to carry around than a laptop and bigger screen than a phone.
8) Not bad for games too if you're not an AAA gamer.
9) For writing articles, book, etc, it's also good -- non distracting, lots of great editors (even Scrivener), and so on.
Same here. I've owned iPads since the very first one for work (app dev), but the closest I've gotten to enjoying using them is watching movies on airplanes. I'm always interested in seeing what other people put them to use for.
My theory has been that iPads appeal to "full-screeners".
I've been a Mac user since 1990 and the Classic MacOS was optimized to "right-size" your windows to your content so you could have lots of windows next to each other for UI affordances like drag and drop. Classic versions of Photoshop had palette windows that hid in the background, even early OS X used "inspector" palettes heavily. Until very recently, MacOS didn't even have a full-screen control. So I've always filled my screens with windows of stuff I'm working on, stuff I'm monitoring, chats, etc. I guess I thrive on info-ADD? If I use an iPad I feel claustrophobic. Made 10x worse by the lack of multitasking (no persistent background network connections, apps continually killed for RAM usage).
In contrast, Windows started out as a full-screen, split-pane OS, and Windows apps have always relied on the "MDI" UI with a containing window, optimally used at full-screen. So most users grew up with that. I see people buy those super-wide LG displays and then full-screen a Chrome browser and complain that their lines of text aren't 2 meters wide.
And kids these days grow up with full-screen mobile UIs.
So if you grew up with everything being full screen, an iPad feel familiar and useful. If you're used to being able to monitor a bunch of windows at once, the iPad will feel like a toy.
Docks are obscenely expensive but the quality of life improvement is high. You're unfortunately very limited with the MBA, though. Perhaps see if you can replace it with a MBP?
I DO like having my "work" machine be a powerful laptop in the event that I need to travel or some emergency arises where I HAVE to find a coffee shop and write a PR without monitors, as much as I won't enjoy the experience.
My desktop is a Ryzen 2700X with 32GB of RAM. I really would like to pickup a TB3 dock at a point but am currently using RDP to my work laptop. Which works well enough over the local network.
What I wanted to respond to was your point about having your work machine be a powerful laptop so that you're prepared. I've been mulling over ditching the desktop for a Thinkpad X1 Extreme for the same reason. While I could remote into my desktop in a rare coffee shop scenario, it wouldn't work out if it were happening often.
So, basically I'm spitballing and have no real answers to your questions, sorry. Just wanted to reply and tell you I'm probably wrong about there being MBA + dock issues.
I used a Dell dock for years alongside my desktop, using 2 monitors to my laptop and 1 for my desktop. I'd like to get a TB3 dock and do that just as you are. And while unlikely at this point, given how much I like my Samsung, I may eventually have a Macbook Air. Which is not the best device but definitely a top tier throwaway easy-chair machine if not a little limited for the money, not having a 360 degree hinge.
Unfortunately there's tons of issues with egpus in Bootcamp installed Windows. I didn't realize it'd be so drastically different from a vanilla install.
I loved my old Samsung S9 laptop. That thing cost a small fortune but it was so powerful for its size.
Not that this is totally up to taste. Some people love working on a single smaller monitor, with only a full screen editor or some terminals. More focus.
(I used to love it too, but I can't stand the modern MBPr keyboards, so I connect it to an external keyboard and monitor now. Note that I love the external "Magic keyboard 2", it's just the built-in laptop keyboard "butterfly" that I find crap).
A friend (age ~30) works on very large-scale climate model comparisons. He directs his model runs (done on a remote supercomputer, which is his version of a "real machine") from his 13" Air. I work with smaller datasets, and it's kind of amazing what power he can command from that little thing.
He uses a dock to make visualizations on a larger monitor when at his desk.
I have no idea what the appeal is, there's none at all for me, but there must be a decent sized market out there. It's interesting to read the other comments and see what the appeal is for them