I couldn't care less if these laptops came rainbow colored with pink unicorns and butterflies painted on every surface. Only the specs and long-term reliability are crucial, and that's all I need from what is merely a tool.
And the reason behind why quad-core laptops should pack a dGPU has little to do with demand but more of a question of "why not?". As pointed out, a few business laptops (Lenovo Thinkpad T470p, Dell Latitude 5480,5580 and more) do come with the quad-core CPU and iGPU combo. But high-end multimedia laptops (Dell XPS 15, Apple MBP15, Asus Zenbook Pro, Lenovo Yoga 720) and light gaming laptops (Gigabyte Aero,P3Xx, Aorus, Razer, MSI GS) are more cost efficient due to their similar weight whilst packing dGPU and much superior thermal solutions.
Lenovo, Dell, HP, Fujitsu and Sony all have the best business line of laptops. However, they've never really specialize in gaming, and thus aren't equipped to handle even regular 45 watt TDP, hence why they're all set to 35. Besides, I think even regular dual-core systems should have a 1030/40 dGPU by default. These days, too many ODMs are just robbing tech-illiterate consumers in plain sight, with those ridiculously expensive thin&lights that don't even have decent battery life.