The Gvido sheet music reader is discontinued (and was super expensive). Other eink displays are also super expensive, and non-eink tablets tend to be too small, maxing out at around 10". The Yoga Book 9i with dual 13" oled displays could be tempting but is again overkill to get a $2000 device just to read sheet music...
Why the iPad? There may be an aspect of "nobody ever got fired for buying IBM." If your iPad fails or runs out of battery (it happens), other people will be sympathetic. If you bring something "weird" and it fails, it will be because you tried to cheap out on something weird, and it's your fault.
You'll get less screen area than you might expect unless the screen has the same aspect ratio as typical 8.5x11. I own a 10" tablet that's sufficient for reading lead sheets (melody plus chord changes) but am seldom motivated to actually use it. I already know most of the standards that are likely to be called on a gig.
As for why an iPad, I think it’s more that either folks already have iPads, or they get them because “creatives” like using apple products. Same reason musicians will often get a MacBook instead of a dell even if they don’t need it for any particular reason. Both of those reasons would lead to the network effect of folks asking their friends/colleagues what they use, and then buying an iPad because of that.
My other band, a quartet, is more like what you describe. And anything new is going to be in digital format.
I'll probably end up upgrading soon just so reading sheet music is more comfortable. And it is much cheaper than $2000 (It reaches almost $2k with the 1TB + Apple Pencil, but starts at like $1.1k). No dual displays though.
I'm not sure if it qualifies as lightweight, but if you are referring to actual weight, it seems to weigh around half as the Yoga Book 9i and a bit more than double the Gvido sheet music reader...
The Air weighs 1 lb and it feels fine when holding it up during a performance, the 13" Pro weighs 1.5 lb.
I used Forscore and have a bunch of fakebooks and custom charts on it. Even with a regular stylus it's been very useful (though I occasionally wish my 1st gen pencil had not died).
If I had to replace it I don't think I'd bother with a super new one, as this is plenty of horsepower / memory for the things I use it for. So probably way less than $1k, I'd think.
You are right on the horsepower, might also be worth getting a refurbished one instead. But I've ended up using my iPad for way more than just reading music so I'd get the new one if I was shopping atm.
But probably doesn't quite fall into the "lightweight" category...
I doubt I’m alone. But I also doubt I’m alone in buying the 12.9” pro just for having the giant screen on an iOS device. So they might be smart not to make that option.