I don't think you're making a fair comparison there really. You should be comparing Apple to someone like Dell, HP, Asus, etc.
What you're really comparing Apple's support to is your own, because you're the one building and maintaining that PC's hardware. Plus take a look at your 10 year old PC, does every component of it - motherboard, GPU, etc. still get security updates? Motherboards are one of the worst offenders in this area for just arbitrarily dropping support.
The fact that the PC ecosystem is so open is why it can last so long, but I don't think it's as imbalanced as you're suggesting.
Disclosure: I don't own any apple products