I always encourage people to use Job because LR makes this field so easy to filter or use in smart collections.
Yes, adding a job can duplicate some information, but that applies to a lot of the metadata we commonly put in LR fields. Keywords or titles can often duplicate the info in the folder name or file names, but each one allows us different ways to search in LR and more flexibility over search criteria.
Imagine a job photographing an event over a few days, maybe over a period, so for instance a wedding job from the "2024-01-24 Jones Watson engagement party" folder and other folders up to the day itself. Making the Job "Joe Jones and Lucy Watson wedding" means you can name individual folders as you want - with shorter and more readable names, for instance, or more accurately describing a day "2024-09-24 Joe Jones Riga stag trip". You also got just a few shots of the city which weren't really wedding/client-related, so maybe leave the job empty for them? That's quicker than creating a new folder for those few images, if that's what you might do, and maybe next week you'll change your mind and one or two of those photos helps tell that day's story. Folders are meant for storage, and they're inflexible as a way of categorising pictures.
Later you want to gather all the job's photos, and a smart collection gathers that job's photos with Job / Contains All Joe Jones and Lucy Watson wedding. Now, each time you want that job's photos, you don't have to type Jones Watson into the Folders panel's filter box, and then filter out the non-wedding photos. When you want to create a portfolio of your best wedding photos, you might filter on 5 stars and the wedding keyword, and then another Library Filter column is the Job so you can see you're not including too many from one event or wonder why a job is missing (because back then you used 4 stars for the best?).
It all goes back to giving yourself different ways to search and more flexibility over search criteria, and it's easy to overlook how Job is one of the few fields that LR makes fully searchable.
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