Darth, there's no way this is "Apple's last iMac" - it's a great machine for the demographic needing it. It's just too bad there's not one in black to match your evening wear.
Regarding advantages "over an MBA with monitor", I would say for sure, yes, an iMac in use has the following:
(1) it feels less wasteful when chosing to use a custom or larger keyboard and/or trackpad/mouse combination when using an iMac vs a laptop;
(2) the installation of an iMac or an iMac + external display looks and feels more permanent in an office, studio, or lab environment;
(3) if being used by people who might damage a laptop by spilling drinks on it or dropping Ritz cracker crumbs in the keyboard all day long, iMac with external keyboard wins by far;
(4) if in an environment where someone might try to walk away with a laptop or play with plugging and unplugging cables, iMac is easier to secure in my experience;
(5) better not having to look/shift focus between a relatively large external display and a relatively small MBA display when using the Mac for daily office work over extended periods (laptop in extended display mode);
(6) the ability to have more desk space available if using the iMac, especially when VESA-mounted;
(7) the ability to have two floating displays of similar external dimensions when pairing an iMac 24" with a Studio Display/LG UltraFine or similar, especially if both are VESA-mounted; and
(8) the price of a 1TB/16GB MBA is going to be around $1900 whereas the price of a similarly-spec'd iMac is going to be $2100 which means you get a way better display for only $200 more.
I have and currently use several combinations of iMacs and MacBook Airs and external displays —and have been doing so for many years— so those thoughts above are just based on my own experience. There are indeed times when an MBA + external display are the best solution, but that wasn't the question I was answering. Aloha.
