People don't equate trackpad quality with a good computing experience. They look at all the things like GPU benchmarks and HDD capacity and make their purchase decision based on that, which is not necessarily a bad thing, different people have different expectations. This is why manufacturers like HP can sell on things like screen resolution (without improving screen quality), and fast CPUs and GPUs while skimping on things like battery life, build quality and the overall experience.
After hearing my friends diss Macs for overpriced hardware and being underpowered, I would say there is little incentive for PC manufacturers to improve on things like the trackpad. People either don't care or don't think to care. Either way, tech reviewers may notice but attention to detail like that just goes unappreciated for the average user.