Mostly, because preinstalled with Windows and then installing yourself is still cheaper than buying from a small, single trader.
I believe those missed the point about Linux. They thought the rage was all about saving the costs of Windows licenses, and they could not survive the aggressive licensing program of the late Windows XP/Vista period, when Microsoft practically gave away licenses almost for free. I don't believe it's about costs. IMHO it's more about freedom.
One person was complaining about custom duties and warranty issues in Europe.
https://news.ycombinator.com/item?id=13364334
As I wrote in another comment System76 does little things such as flash custom firmware and bios to make the computer more Linux friendly.
Yes, twice, very good. Check my other comments for more info. Long story short, the Lemur is an excellent little laptop that replaced two large pieces of crap from HP and Dell. AMD cut support for the graphics a month or so after I bought it, and it always ran very hot. The Dell's usb ports shorted out. I have never had that happen before.
The only problem I have had is with Intel. Intel does not get mature launch support in their drivers until well after launch. My Ivy Bridge Lemur would freeze once in a while after resuming. I do not think it was fixed until Ubuntu 13.04 (It came with 12.04). I had to put Manjaro on my Skylake Lemur to get Mesa 13 to get all the issues fixed. Skylake has been out more than a year, and Mesa 13 came out recently. Skylake has not been as bad as Sandy Bridge, but still a problem.
> some laptop robustness and touchpad / build quality issues
Do not have issues with the touchpad.
Compared to the HP and the Dell I bought the Lemurs handle heat very well, build quality seems very good. The Skylake and later Lemur's have a very sleek, modern look. The Ivy Bridge Lemur has a boxer look that you can see with other laptop models.
I do not know what you mean by 'laptop robustness'. I knocked the Ivy Bridge Lemur onto the floor and it survived. The power plug was off centered because it fell on it's power input, but it was like $20 USD to fix. The shipping cost me more.
My advice to you would be to always request the latest Ubuntu.
Edit: to clarify, desktop might range from dirt cheap commodity hw to high profile workstations. So no blades, rack-mounted stuff etc. (I don't know what fits your definition of server).
Linux offers could work for people just wanting a working computer with less risk of viruses. People that don't care for their machine running Linux. Most other people interested are tech savvy and will compare other offerings as well or selfbuild.