What observable characteristics of a spot of land make it industrial in our eyes? The factories, certainly, but also the equipment strewn about, the disorganized patches of paved and unpaved surface that no one bothers to landscape, the expectation that pedestrians usually have no business there, even if they’re legally permitted, the noise, the smell, and so on.
there are different types and scales of industrial landuse, huge plants (and a whole grid of private streets typically without public access, even private railroad access) e.g. automobile production, steel or big scale chemical industry, and smaller scale areas with one or more typically several sites, with streets between and maybe commercial and retail use nearby (car dealerships come to mind), where sidewalks are not uncommon around here. Nobody would want to live near a chemical or petrochemical plant, but a small scale electronic manufacturer or apparel manufacturer is not an issue.
Yes, these are all just examples of characteristics. I certainly wouldn’t make them all requirements. For example, I live a stone’s throw from a brewery that is well-kept and even hosts the neighborhood’s farmer’s market on weekends, but a distinctive scent and sound emanates from the plant during some times of year. Without the ability to map the brewery complex as a landuse area, we’d fragment the site between the factory, the storage yard, a parking lot, and some miscellaneous structures. This is just a small plant, all that remains of what was once a sprawling manufacturing district, and the zoning also reflects this reality.
I used to live a stone’s throw from a very different industrial site, a fireworks factory that consisted of a number of small trailers spaced far apart across an open field, as a precaution against explosions. The landuse=industrial area that I mapped in OSM could have qualified for a man_made=works tag, technically, but I would not have reduced the industrial area down to a multipolygon of buildings separated by landuse=meadow.