For me, its politics. Since the 90s, Intel and Nvidia have "cheated" a lot -- at the expense of reasonably "fair" competition. Some of this has been proven in court. For example, AMD was awarded 1.5 Billion dollars from Intel -- thing is, the damage had been done and sealed AMDs fate.

That cheating cost customers choice and money.

Being old fashioned (literally as well as figuratively), I merely don't want to "reward" companies like that.

However, that's just me. Other folks either don't know the "back story" or don't care. And, that's okay with me

With graphics, being an AMD fan is easy -- Nvidia and AMD switch places every few months -- both are hyper competitive.

With desktop CPUs, its getting hard -- AMD has not kept up. Still, AMD is competitive. That's probably because Intel is not going "all out" to develop desktop CPUs. Rather, they seem to be after "similar performance" at "lower power" -- which is a good fit to the current Market.

In summary, Intel and Nvidia make great products. Were it not for their history, I would be buying their stuff at times -- and don't begrudge others buying their stuff