There can be ONE reason to not touch it . . . dry rot. Especially with the fabric headliners. What might start out as "just a little spot" can turn into a full-blown replacement, VERY possibly.
On my '80 Newport (with the foam-backed headliner fabric), I was just using a vacuum very gently and it was too much for the deteriorated foam, so I ended up just pulling the fabric down. Leaving the remnants of the foam on the backing board. Similar a few years later on my '77 Camaro, except that the fabric on the Camaro was perforated vinyl.
So, even though you can be very gentle with any cleaning activities, you can end up needing a new headliner installed in a year of so. Unless you might opt to just removed it and the bow wires now.
Just some experiences,
CBODY67