Not a complaint, just curious. 

Occasionally I receive a book that is wrapped like a present in plain paper (not plastic & not the PBS 2nd sheet), then placed inside an envelope that is addressed & stamped.  Since the inner wrapper isn't plastic and has no markings or emergency address, I'm kinda curious why some members do this...any ideas?
 

Maybe just for extra protection?

Pam

Probably additional wrapping for extra protection.

I've recently gotten books wrapped like that too.......I'd appreciate a plastic layer, but I don't understand what good extra paper does.

If they're putting it in an envelope, then maybe it's t keep the book from opening and getting all bend up by sliding around loose inside the envelope. I've had a few come loose in manila envelopes and the pages bent from sliding, and one cover torn loose (I suspect it already had a rip in it) while traveling. I had one come loose like that, only with two rubber bands on it to keep it closed. It was okay, so I guess it worked.

If they're wrapping the envelope tightly, maybe it's just habit?

I'd appreciate a plastic layer, but I don't understand what good extra paper does. 

Unwrapped books can get trashed shifting around in over-sized envelopes. Pretty much any time I receive an unwrapped book mailed in an over-sized envelope it has been beaten to crap. One arrived accordian folded.

For whatever reason there are members who refuse to plastic wrap. If they will not use plastic I'm grateful for the paper wrap. 

The outer wrapper was a bubble envelope, not much bigger than the book (a good fit).

Interesting replies, thank you!
 

I think that a paper wrapper inside the mailing envelope provides additional protection/padding that a plastic layer alone does not provide. Plastic does indeed help books from water damage, but additional paper layers inside the envelope also help protect books., especially if the envelope is too large, not folded over and taped, and the book is able to slide around inside.

I've been known to wrap light cardboard or something sturdy and tape it around the book before adding an outer wrapper, to support the spine and/or book pages/corners. 

But this (in particular) was a very thin piece of paper lightly taped in a couple spots.  I guess it could have added a tiny bit of protection, and maybe prevented bending corners or cover while inserting into the envelope.

A thin piece of paper lightly taped in a couple of spots is not going to add significant additional protection. It would have to be more substantial than that to make any difference.