The big issue is that most customers, retailers and laptop makers associate AMD with low-end products. I got a 17.3-inch laptop since 2009 with AMD RM-75 processor and dedicated HD 4570 graphics. I got it as a desktop replacement for office work/music/movies, nothing more. I even tried a few games on it - it can handle some big titles up to around 2012 as long as it's placed inside a room with up to 16-18 degrees Celsius. If the temperature is above 20, then CPU will throttle in less than 10 minutes of gaming. Oh, it's an Asus, one of their worst laptops ever if you read the reviews - but mine works fine even now and never had too big issues with it. Nevertheless, build quality is very low and most people looking for mid-range to high-end products wouldn't even look at AMD after all this time.
P.S. I only used AMD processors in my builds for about 15 years since my first computer back in 1997, but I left them behind in 2012 and it's going to take A LOT for them to make me come back. Talking about laptops, a fanless design with decent juice for light multitasking in office/movies/music tasks would definitely do the trick. For my main desktop PC... I just can't imagine what they have to come out with to make me drop Intel.

Being the owner of a Lenovo Z50-75 with FX-7500+R5M255, I am starting to think these configurations are only released to undermine AMD's (non-existent) reputation.

The Lenovo machine is cheap, but houses THE WORST display ever made in human history. HP placing an absolute low end dGPU beside a 768p display... this resolution should have died 3 years ago, but any AMD APU could handle this resolution. The dGPU only wastes power and decreases battery time.

Why oh why can't notebook vendors make PROPER notebooks based on AMD hardware?

For instance: Lenovo Y45? Carrizo-L+R7M375 with dual-fans, 14" 1600*900 IPS, 2,5" or mSATA drive. This would still be a mid-range notebook in terms of price, but it would be comparable to the overpriced Razer/Alienware machines in terms of performance. (At least in proper DX12 games)