Who is this for? Someone who wants a computer. Ah, but take away the people who want multi-monitor, take away the people who want mechanical keyboards, a bigger fancy monitor, and what are you left with? Still basically everyone!
And it's not like this is the only computer Apple makes. They have 1 basic hardware platform based on the M4, they give you the laptops for portability, the iMac as the basic desktop, the mini for if you want to do all the things that the iMac isn't configured for, and they have the Mac Pro to taunt professionals. It's an incredibly coherent product line up. No one is confused about which one they want.
Oh and by the way, it works really well for Apple too, because they are literally just taking the guts from their other products and sticking it in the same design desktop they've had for years. Do you really think that'll be improved by redesigning it and therefore charging 50% extra due to all the bespoke costs?