Do you think that Apple specifically doesn't offer dual monitor access on the MBA, to convince consumers to purchase the MBP?
its a pcie/memory buffer limitation.
It's absolutely a hardware limitation, but one that Apple has engineered in by-design. Partly that will be cost control to keep the MBA price down, partly it will be what
@circatee suggests to up-sell some people.
IMO it all makes sense. The MBA is the laptop you buy when you want a very good laptop. It's the default choice as it does so many things brilliantly.
But, the moment you say 'ah, but it doesn't have / do...' or 'yeah, but I need / want the better...' you're into MBP territory.
The majority of MBA buyers won't regularly want to connect multiple displays. They also won't truly take advantage of the better screen, or additional ports, or other MBP-specific advantages. The MBA has taken the place of the old plastic model MacBook's, which were the default non-Windows choice for many people and satisfy most peoples needs without spec'ing up too much.
There is absolutely an audience who
want those the MBP improvements in the body of an MBA, I'm one of them*, but I don't
need them, it's just a preference.
Once you get to a need, or you have a buyer who is willing to spend more money on their own preferences, Apple want you to step-up into the MBP models.
(*Give me a 13" M2 MBA with the ProRes screen, slightly higher resolution, and Centre Stage on the camera please. Take my money!)