Because iPads are fundamentally different than laptops. Workers use tablets in the field all the time, often for shorter, quick, one-off checks and such. If you're in a fleet truck or on a job site, having a tablet on the passenger seat to check on work orders is easy. Pulling out a laptop is a much bigger pull, and more awkward.

Apple traditionally keeps a simple line-up of 3 or 4 models per product category. And each product has limited simple upgrade options consisting of normal vs expanded ram/storage/cpu.

Could they technically create 300 models with every permutation? From cellular, to touch-screen laptop, oled/led screen, different ports, battery sizes etc.

Sure, but they'd be confusing their customers with a complicated product offering and adding complexity in their supply chain hurting their margins, to pursue ever smaller niches that don't improve their bottom line, while competing with small niche brands that already cater to this demand.

And what's the point? You have cellular on your phone and a $3 usb cable plugs it into electricity, meaning you already have cellular for your laptop. You can buy dedicated cellular hotspots the size of a Airpods case that you can throw into any bag, jean or or jacket pocket.

Now if a cellular modem was a $1 part, sure, throw it in there. But it's not, again if you look at industry prices it adds between $100 and $300 to the retail price.

A $200 price bump makes sense for a common need, not for a niche use for an entry-level laptop model, in fact raising the price of an entry-level laptop by $200 is absolutely nuts for a minority use. Niche users can plug in their phone or buy a dedicated hotspot. You say I have a city-centric view, sorry but I don't know if you're not familiar with the typical macbook air buyer. Southpark did a satirical episode about them and it's not far from the truth.

Macbook Pro would be a different story, but this thread is about the air. I do think they'll introduce it in the next 2 years because Apple started to build its own modems. Previously they'd basically increase their entry-level product by a lot just to offload the majority of that price increase as revenue for Qualcomm, it was an entirely bad business decision and no surprise they didn't take it.