My guess would be; if it was perceived they weren't needed (couldn't predict 1Gbps ethernet) it was simply quicker than stripping them and terminating them properly.
In my current place of work, when the building was originally flood wired ~25 years ago, the (IMO short-sighted) decision was made to have dual ethernet sockets with a single cable going back to the patch panel and each socket using 2 pairs of wires.
This limited us to 100Mbps ethernet and I suspect caused us cross-talk related problems due to untwisting the pairs somewhat in order for the wires to reach each socket.
Only this year have we replaced most of the original cabling with fibre back-bones and replaced the copper that was left with properly terminated Cat 5e.