The following addresses the above question from the context of both an iPad as well as the original 12" rMBP:Realistically though, what tasks are you going to be doing on a 12” notebook that you can’t do on a 11” iPad paired with a keyboard case?
A 12” MacBook is never going to be heavy duty/pro device. And with an Apple Pencil, editing images, video, etc is all going to be better on an iPad.
A iPad is just an all round more capable device in that size range now. Even if it’s not yet a total laptop replacement for everyone.
A photographer at an event who may be presenting on a projector, while pulling images off the last SD card that they pulled from their camera. While plugged into power.
Using a mouse with any other peripheral - monitor, projector, wired printer.
Using two external monitors at a time (doable with M1, but Apple doesn't want you to...)
Using power with any peripheral, period.
I personally understand that a small, lower power device will have compromises - but having no (or only one) free port when plugged into power is a huge turnoff for me. I think two TB3 and MagSafe is the lowest I would consider. That alone makes the new MBA much more attractive than the 13" MBP. If I'm at a conference/meeting all day, or in a hotel for more than a couple of days, I want to be able to plug in power, a wired mouse, and an SD reader or a USB Flash drive without having to swap out plugs.