It doesn't help AMD marketplace when so many Users are having issues with their AMD GPU Cards right out of the box due to either poor AMD Drivers or GPU hardware configured too high in some of the hardware parameters or by buggy vBIOS version by the GPU manufacturers.
Word of Mouth is a very strong indicator whether AMD Market will increase or decrease or stay stagnant.
As an example, an unhappy AMD User here is unable to get his GPU to work correctly and switches to Nvidia and everything is fine. That User will now go and mention his unhappy dissatisfaction with AMD GPU in other forums or with friends and family and his positive experience with Nvidia. It is like a slippery slope.
But I am sure there are more AMD Users with positive experiences than negative ones. But the negative ones are the ones that get the most exposure.
Of course the opposite is true also. Nvidia User can also have a bad experience and switch to AMD and do the same Word of Mouth publicity. But Nvidia has a huge Market share so if they lose a few customers is not that big of a deal for them.