Because those employees cost a lot of money and these commodity widgets have razor thin margins that don't enable them to pay high salaries while also making enough profit to stay in business.

You can pay more to hire better people and put the extra cost in the price of the product but then HP, Lenovo, Dell, et-al aren't gonna buy your product anymore, they're gonna buy instead from your competition who's maybe worse but provides lower prices which is what's most important for them because the average end user of the laptop won't notice the difference between network cards but they do check the sticker price of the machine on Amazon/Walmart and make the purchasing decision on that and stuff like the CPU and GPU not on the network card in the spec sheet.