Putting things into categories is hard.
Marketers put customers into categories all the time, must do so, or business would be unscalable and impossible. Sure, in some ways each customer is a unique snowflake, unlike any other, and at some level deserves custom treatment tailored specifically to them, and resulting in a product portfolio that might be unlike any other. But realistically, in order to have any sort of economic efficiency at all, on which to found their business, Marketers really have to communicate with customers and bring products to them in groups.
Sometimes even the slightest differentiation is enough. I have worked on brands that sent out email newsletters, and divided the recipients into just two groups. In one case, the first email to a new customer was different that the regular monthly email the rest of the subscribers received. In another, the product was meant for people going through a particular phase of development that lasted, on average, only eight months, but definitely had a beginning, a middle and an end (the target age group for this product was between 3-5 years old, so that might give you some hint about what the product was). Another separated customers into large and small, with five pieces of equipment being the cutoff.
Why five? What was so different about someone who had six pieces of our equipment that they needed a completely different message, and why did the owner of six have more in common with the owner of 10,000 than with the owner of four? The boundaries of market segmentation are where the artifice really starts to show. The difference between someone with four and someone with 10,000 looks like an actual, verifiable fact of the natural world. But five and six? There you can see more clearly the stroke of the very human and arbitrary pen that drew that line.
I first dealt with this issue long before I worked in Marketing. I was in Philosophy grad school, in a seminar on John Locke, the famous Empiricist. The school of thought to which Locke belongs believed basically that nothing of the human mind is inborn or present innately, that all mental processing is learned from experience, through the senses, of the world. So, the child is not born knowing the concept of "redness", the idea of the color red in the abstract. Instead, a child sees an apple, and then a rose, and then maybe a fire truck or a stop sign. Each thing makes an impression on the child's new mind, like an object being pressed into a mold of wax. But after having several impressions, the child starts to compare them, and notices that the apple and the rose, while different shapes, share a characteristic in common. And the name of that characteristic is "redness", being red in color. The child's mental concept of red, the child's understanding of what redness is, is based on experience, and then abstracted from it.
I remember many debates about Empiricism and perception and mental categorization, during this period of my life. I was a big fan, at that time, of the idea that minds were blank and formless, and shaped only by experience of the world (a point of view I've heard people say is naturally popular in a culture where at age 18 one separates from home and family, goes off to college and imagines one can break completely free of one's past and invent oneself anew). I ran the argument that the categories with which human beings understand and talk about our world are completely arbitrary, made up by us, superimposed on the world but could all be otherwise. A teacher of mine was much more a fun of the idea that our words for things and our conceptual categories that go along with the words "carve nature at the joints". I remember one fierce debate, over coffee, about the fact that our word "table" picks out the table, and not the tables plus the surrounding two inches of air. I thought it could very well have been the table plus the extra area around it. I have softened somewhat on this stance in my later years.
But categorization is still hard. Even though there seems to be a distinct difference between customers in the Construction sector vs the Manufacturing sector, a difference based on real, kickable stuff out there in the world, what do you do with companies that mass-produce the same metal house frame over and over, or companies that produce trucks used in mining that are so large that you can only produce one in the time sometime might take to put up a bridge? There's an emerging field that calls itself MRO, for "Maintenance and Repair Operation". But what is a Repair Operation? That one can be vexing. Do you put Repair in the same category as Construction because they typically only do one unique job at a time, and sometimes do it outdoors? Or do you categorize them by what it is they are repairing, which could be fences out on a ranch property, or hot rod cars, or airplanes, or ships?
John Locke would say, go talk to lots of Maintenance and Repair Operations, and then think about your impressions of them and see what they have in common. But be ready for the next one you meet you change your idea.