I'd argue that in Apple's case, a company with a (long) history, they could not afford not to focus on packaging while positioning themselves as the kind of brand they wanted to become. Higher stakes and with Google/Android a potentially dangerous competitor (whose strategy only became very evident later, ie. not wanting to compete on hardware as well). Now however, especially due to the profits they're making, they have little incentive to care about anything else but maintaining status.

Why change something not visibly broken?

I disagree that non-luxury packaging automatically means the company doesn't care about the product contained inside. It's a matter of strategy & costs. I'm not familiar with HP packaging, but you should know that ASUS does offer luxury packaging for its gaming range of products for instance, especially laptops.

My opinion is that it's possible to design thoughtful, non-generic packaging without crossing into luxury materials territory. Experience and loads of creativity are required though. At least this is what I understood from the article (taking into account the Pencil example as well), that startups should bet on resourcefulness instead of throwing money in non-priority directions.

Another aspect to consider: I don't have the specific numbers to back this up, but we live in a world where the general trend is towards minimalism and simplifying our lives, which includes getting rid of no longer necessary stuff, such as a product's temporary home (packaging). Considering it has such a short life, it makes little sense to invest a lot of resources into packaging as a startup, unless you're selling electronics, where at least some consumers have a habit of saving the packaging materials to increase resale value of the product when they decide to upgrade.