I'm pretty sure that the answer comes down to one word: Superfish.
Although, in my opinion, I wouldn't trust any laptop hardware company out there enough to use the system that came pre-installed with it, but that's for another discussion.
There has been a string of things, including Superfish.
There was also the Lenovo Solution Center problem. And the Lenovo BIOS shenanigans (or was it the Lenovo Service Engine?).
There have just been too many lapses in judgement at Lenovo. Either their competence is slipping or their ethics are. Either way, I'm done with them for now.
I prefer a great deal plastic to environmental foe aluminium. To me their use of aluminium is a very good reason not to buy Apple hardware. I have a Dell M3800 right now, and the build quality is very good. Thin, light, excellent 4K touch screen, good battery life, I easily added a second HDD to it. Not to mention that every thing works perfectly well under Linux.