Laptop manufacturers could also just avoid this problem by using modems that don't require proprietary drivers or firmware, like those from Intel or Atheros. This is an entirely avoidable problem.
Certainly they can try to push the "Sell laptops with Linux preloaded and make sure everything works" approach (because let's face it, that's pretty much the only reason why Windows laptops are pervasive), but if you're trying to increase the number of people using Linux, I'd suggest that they might get better results as the thing one uses to repurpose their existing laptop.
Linux support isn't 100% perfect for me, by the way, but it's very usable. The main problem I still have is that power management is mediocre (I can't get it below about 8 watts idle generally), and the USB-C dongle you need for ethernet is very flaky under the current kernels. It works, but often requires unplugging and replugging for it to be recognized, and (very) occasionally completely hangs the machine a few seconds after I plug it in.
(I do think it's fair to call out Dell for selling a Linux developer machine that can't even connect to the internet without proprietary drivers. There's no Ethernet port either.)
On the plus side, the retina touch screen works great. Even on my custom NixOS setup it gives me smooth scrolling and even pinch-to-zoom in Chromium Google Maps. Pretty cool.
The Intel cards are nothing to write home about, either. Their only redeeming qualities are the availability of a free driver and Just Works experience in Linux. Otherwise, they are quite slow - so I understand why Dell puts Broadcom into Windows version.
Additionally, I was fine running Windows 10 at first and doing all my dev work in a Fedora VM, but the Anniversary Update has pissed me off considerably, leading me to want to migrate to a bare-metal Linux installation.
No real problems so far, except the ones that were caused by me because it was the first time I've ever set up a linux on a laptop.
If you want something a bit bigger, but that just works, the E5510 is excellent, especially once you have Ubuntu 16.04.1 (or a distro with the 4.4.0 kernel) on it.