To be frank most people are basing their memory requirements based on x86_64 PCs, which is a poor comparison to these ARM machines.
We know from web browsing on iPhone/iPad that even with 2gb, Safari can make many tabs feel comfortable.
I think Apple wouldn't be selling a machine with 8gb if that wasn't enough for most people.
Here's the perspective of someone who has been using Macs with at least 16GB: it's not about whether 8GB is "enough" or not. It's more that...
...this is a computer, with many things running concurrently in the background at all times, unlike the iPhone or iPad, which only run one app at a time and are now having 4GB and 6GB of RAM respectively.
RAM is not cheap, but it's a necessity if you know you'll be running high resolution stuffs. Websites now load high resolution photos and assets, and even PDFs have embedded vector graphics or high resolution photos.
Is memory requirement on x86_64 unrealistic for ARM? I don't think so. Even if it's unrealistic, consider this scenario:
I have MacRumors.com, Facebook.com, and Capture One 21 open.
Notice I've already hit 10GB of swap usage even with 16GB of RAM, and all I'm doing are photo editing, web browsing, and emails. What magical thing will ARM allow for that will make this scenario any better? I haven't even launched up my IDE or started Fusion 360, either...
Again, the iPhone and iPad are poor comparisons because those only run one app at a time. They allow for certain (limited) services to run in the background, but apps are not allowed to run in the background for too long in iOS, so memory is more tightly managed than on Mac OS. RAM requirement is going to blow up on Mac OS, which is precisely why 16GB RAM is offered, and also precisely why some are asking for 32GB options.