dpb writes:
Scott Lurndal wrote:
...

IIRC, the purpose of the tape is to force the threads together more
tightly.

How would possibly physically do that being so soft as compared to metal?

What it does is simply fill voids as does pipe dope in a more convenient
form factor...

--

Memory confirmed by Wikipedia:

One of the defining characteristics of PTFE is how good it is at defeating friction.
The use of PTFE tape in tapered pipe threads performs a lubricating function,
which more easily allows the threads to be screwed together, to the point of deformation,
which is what creates the majority, if not all, of the seal.

scott