The 17" doesn't exist because it wasn't a good seller and because with the advent of the HiDPI screens the 15" could take over its niche (high resolution). The 17" was never more performant than the 15" model. Eliminating the 17" option is a simple action of streamlining. I do not understand how this can be interpreted about "not caring". Apple throws insane amount of money into researching new materials and manufacturing techniques for its laptop line. If they didn't care, they'd just use the old chassis and plunked in newer CPUs, instead of trying to come up with something new.
If you look at the overall computer market, the 17" is all but gone. Modern laptops are using 15" form factor max. The 17" is only remaining within the desktop replacement and gaming laptop market, and even there the 15" is the most popular option. Ah, and yes, you can also find some 17" laptops in the budget market, because they are cheaper to make nowadays than a 15" with the same specs.