Why are desktop and laptop PCs still so reliable, whereas cellular phones are engineered to wear quickly?

I know why cellular phones are engineered to wear quickly. The reason is simply to force the consumers to buy new products. It's called "planned obsolescence". My question is: why don't the legacy PC manufacturers adopt the same policy? I remember Intel once granted, or still grants, a lifetime warranty on its CPUs. What about GPUs? I have less or almost no experience with graphic cards.