A simple understanding of cognitive functions might help here. Essentially, people are either governed by judging functions or perceiving functions in either their inner or outer world. Judging functions consist of thinking and feeling, while perceiving functions consist of sensing and intuition. For those with extraverted judging functions (Fe and Te), the external world will be a place of structure and organization. For those with extraverted perceiving functions (Se and Ne), the external world will be a place to primarily gather more and more information, which often results in procrastination, indecisiveness, and a lack of action. For those with introverted judging functions (Ti and Fi), organization and order will occur within the mind, in the inner world of either thought or feeling. For those with introverted perceiving functions (Si and Ni), the inner world of the mind is where new information is constantly taken in.
Given people often have both an extraverted and introverted set of judging and perceiving functions (called the dominant and auxiliary), a person will either come off (out in the external world) as either organized and orderly or indecisive, low energy, and unstructured. Those who come off low energy and unstructured (Ne and Se) will often have introverted judging functions (Fi and Ti). Those who come off organized and orderly (Fe and Te) will often have introverted perceiving functions (Ni and Si). Ultimately, those with extraverted judging functions are known as "Judgers," while those with extraverted perceiving functions are known as "Perceivers." Hence, judging and perception.
Thus, as INTPs with introverted thinking (Ti) as our primary function and extraverted intuition (Ne) as our auxiliary function, we will engage with the outside world in a very unstructured, low energy, non-serious manner. But in the inner world, within our minds, there will exist lots of rumination, organization, order, and structure, as we constantly take the information coming from our Ne and endlessly attempt to make sense of it, in a way which is very grand and coherent. Hence, we often called "The Architects." We love to build thought.
So basically, as we have an extraverted perceiving function (Ne), we will simply engage with the outside world in a way that is very laid back, unstructured, and so open to starting projects that we tend to never finish them. This basically explains our often extremely low energy, where we can manage to sit around for hours doing nothing, while work perhaps seems like a dreadful chore (and clearly, this explains our often lack of work ethic). And yes, because we have introverted thinking, we will often think for hours and hours trying to solve problems and work out schemes rather than actually go out and take action immediately. As a result, we are not "doers." We are thinkers.
And as far as I know, introverted thinkers are often notoriously known for "explaining away unnecessary work." This is a hallmark of introverted thinking, as this cognitive function is aimed towards doing the most with the least amount of effort. Here's how it's specifically worded by a well-known cognitive function test: "Apply leverage to a situation to solve a problem impersonally using minimal effort." Essentially, if we don't see the logical need to do something, we'll scrap it, and we'll stand by our decision while everyone else continues to believe action is needed.
Also, there's a facetious movie about Einstein as a young man in which a series of problems are occurring in his immediate environment. But as everyone else is panicking and running around frantically, he is just sitting there, thinking in silence. His girlfriend then says, "l'm sick of brains! All this thinking all the time. Think, think, think. I want a man who will do something."
And that... is pretty much INTPs in a nutshell. Are we lazy? Yes. Is it a bad thing? While it isn't a good thing to be lazy, we simply often lack the energy and psychological inclination necessary for organization and meaningful action. So I can understand why humans use the word "lazy" in a pejorative fashion, as it's clearly a detriment to humanity. But in the end, we should not feel bad about the fact that we just aren't the type of people, generally speaking, who organize and implement. We are very low energy thinkers who often work in worlds of abstraction -- not reality. And I don't know about most of you, but I'm the laziest person I know. Putting mental energy towards even the most basic task if I really find it to be of absolutely no interest??? Hell no. I get others to do it. Having physical energy to clean all day? Hell no. I shirk my physical duties all day. Thinking, thinking, and more thinking within my head for no actual practical purpose at all? That's all I do.