Why don't word processors have tabs like spreadsheets?
At my job we have work procedures in a spreadsheet and it is valuable to have extra information about stuff on different tabs accessible by a link in the procedure.
Why can't that be the case for a word processor?
Something like that was tried with a word processor created in the 90s called Yeah Write, but it never really caught on. Maybe there isn't much demand for that, especially for the use case you mentioned.