> Copy-pasting code that you don't understand is pretty much the definition of laziness.
Disagree. Copy-pasting code that you don't understand is how most people learn how to code on the web. It's how I learned.
Most junior web developers do not understand everything that goes on in the web stack. They piece together the ability to run a functioning website by putting together bits of knowledge they pick up along the way. Some of this knowledge comes from reputable sources, like the jQuery documentation. Some of it comes from sources that may, albeit wrongly, recommend hotlinking, such as friends or Experts-Exchange.
When you're new to a subject, and there are that many unknowns, and you don't have a great mentor, it's hard to know exactly which parts are important to understand thoroughly, and which can be attributed to "magic" for the moment. Most people learn to program for the web because they need to get a project online, which means they are more focused on getting something working, rather than trying to grok every bit of the stack. I would bet that the vast majority of people that hotlink jQuery fall firmly into this category. It's not that they don't want to learn how not to hotlink, or are too busy or too lazy to learn, it's that they don't know that this is something they need to learn.
And that, sir, is definitively ignorance, not laziness. To be precise, it's ignorance of the fact that they are ignorant.
PS: Don't take disagreement personally, and don't call the person you're disagreeing with a "Hallmark card". It makes you look like a troll.