The best selling is the base model because it's the cheapest. Majority of users won't do much past web browsing/emails and general use.
It's why I believe the best model to get for the MBA IS the base model for such use. There's no need to spec up a MBA for that kind of use, which fits majority of people. If you're going to spec a MBA to 16/512 because you need the power for your workload requirements, you might as well head towards the MBP 14.
That's just my opinion though, to all their own.
More storage and RAM might be for use cases that don't need "power" per se.
For instance, I do photo editing a lot and ultimately, that's why more storage helps. Photo editing won't really need "power" per se since 90% of the time, I'm just staring and making some small adjustments here and there. But incidentally, the same task will also need a lot of RAM, especially when I proceed to merge multiple photos together for a panorama.
Sure, the 14" is faster but do I really need to merge panorama within 30 minutes? Or can I wait 45 minutes to an hour for that task to finish? That's the kind of consideration I think you and many others are missing out.
Similarly, the same thing can be applied to coding, video editing, etc...
If my workload needed constant 3D modeling workflow, then yeah, I'd stick with the 14" with its faster GPU. But unfortunately, that's not what I do most of the time, and thus 14" is super overkill still.
Another thing to consider about having more RAM is... I also generally just leave 30+ tabs in Safari opened while I'm doing research. Again, nothing that needs "power" but Safari or Chrome will need all of the RAM the system has for that. Otherwise the browsers start to swap out to storage and slow down when I'm switching between the pages. It's not a big deal when I throw 16GB or now... 24GB at the problem.
So it's not that the extra specs can only be utilized by the M1 Pro/Max in the 14". Any amount of storage or RAM can be useful depending on use case, and it's still all independent of the processor.
Otherwise why even bother going with 32GB or 64GB RAM in some past Intel 15" MBP? Did we forget M2 is actually still faster than many past Intel 15" MBP both in CPU and GPU performance?