Apple builds one machine, with a set of compromises that will appeal to as many people as possible (and they do a pretty good job, if there's only going to be one, with a limited range of configurations).
By contrast, HP makes at least 9 models of 15" (including 15.6") laptops (not to mention the hundreds from other Windows vendors). The lightest is lighter than the Mac, the heaviest can reach 7 lbs plus the power adapter. They have displays ranging from 1366x768 on up to 3840x2160. There are models you can configure without WiFi if you really want to, and there are some with optical drives. You can get anything from integrated graphics far inferior to anything you'd find on a Mac on up to gaming GPUs that will drain the battery in 20 minutes.
Many of us would like to see Apple do the same thing, but they won't. One of the secrets to why macOS runs better than Windows (and it does) is that it supports a severely restricted range of hardware. Excluding Hackintoshes, which Apple doesn't support, the number of permutations of Mac supported by any given release of macOS is probably in the low hundreds. I suspect there are probably more configurations of 15" HP laptops sold today than total Mac configurations supported by El Capitan? All are pretty good hardware, better than 90% of PCs out there, and some are better than that. In addition to "no cheap hardware", Apple also refuses to support exotic hardware (gaming-grade GPUs on notebooks, for example) - they are more trouble than they're worth in Apple's eyes.
A huge percentage of Windows instabilities are related to either junk hardware or exotic hardware - and the tricks required to support those two categories affect the stability of Windows for everybody else. Junk hardware sells an enormous number of units, but makes no profits (Apple sells only about 7.5% of computers worldwide - 15% or so in the US, but makes more than half of the profit - at least on laptops). Exotic hardware sells tiny numbers of units...
PC hardware falls into four categories:
Junk - $300 desktops, $500 laptops, Chromebooks (most of them), most computers sold at Best Buy - You simply can't hit those price points without skimping pretty badly (and making money off of pre-installed adware and spyware), and the machines show it in durability and power.
Standard business computers - Nothing fancy, made to be word-processed on day after day, with some forays into Excel and PowerPoint. They are much better built than junk machines, and their business customers won't accept pre-installed Superfish (really nasty adware Lenovo and others were installing on junk PCs). You can pay $500 to $1200 or so for one, depending on what you want. Pick one up at Staples, but many or most are sold through CDW and other online resellers that businesses work with.
High-end non-gaming computers - At the lower end, these are the choice of middle-class college students and lower-level executives throughout the US. At the higher end, photographers, video editors , engineers and GIS mavens have specialized needs (and the CEO gets one too). Microsoft, HP and even Dell are giving this market a try, but Apple's market share has been estimated as high as 90% and rarely lower than 75% in all personal computers over $1000 (the remaining sliver contains the Surface and all of its friends, workstations and the high-end gaming market). You can pay $999 to $3199 at your local Apple Store, even more for some workstations sold direct by Hp, Dell, Lenovo and others.
Gaming computers - $2000 to $10000+ exotica that are often unstable, but always fast! Yes, you can run Word on one, but it's like driving a Ferrari to the grocery store - almost anything else would have gotten there at the same time, used less gas, and held more groceries. They are really built for one purpose, and their tiny sales (as a percentage of all computers sold) are obscured by the fact that tech websites love them. They are not always more expensive than high-end non-gaming computers, but you'll get more speed (especially graphics speed) and less practicality and stability for your dollar.
Apple plays in the upper end of the standard business market with the 21.5" iMac, some of the Airs and the 13" Pro. Everything else is pretty much in the high-end non-gaming market, which Apple completely dominates. They refuse to play in the junk market (no profits, can't make it stable) or the gaming market.
