In my opinion it’s because it’s unnecessary for the majority of people. 4wd costs more to buy and run (road tax, fuel, servicing?). When you add all of those costs, people may be less likely to buy one. Manufacturers will have done the research to see if there’s a demand for 4wd and there mustn’t be because if there was then they’d be available?
I know there are some awd systems out there that automatically switch between fwd and awd when they’re needed. I’d be interested to see the data on what the average time spent in awd is? as id imagine it will be very little which would kind of support the arguement that it’s unnecessary.
I’ve spoken to plenty of people who just assume that a car is 4wd because of the styling so your friend is not on his own with that one.