I think we have allowed cable manufacturers to convince us that computer data and phone data can't survive together inside the same cable jacket.
its a TIA/EIA standard I don't believe 10baseT was designed to run on "spare pairs as I recall it was separable cat3 also with the same argument about the "spare pairs "
most customers around here went from coax to cat5 wasn't a lot of 10baseT
i was involved in some early discussions on the TIA cat5 standard and I don't recall dual use even being on the table
