I can only speak from personal experience, but I only accept personal check or money order for my sales. Commonly folks ask to pay me via PayPal and I only accept F&F in that instance. It has not hurt my sales at all, in fact, I only have one piece for sale at the moment.
Then again, I do not ever ship large speakers as the OP is correct, these have an increased probability of damage, so I sell these on Craigslist, and would never purchase large speakers that had to be shipped. If I did, I would ship via a moving company, rather than a common carrier.
As a buyer, I am sympathetic to sellers that ask for F&F, and purchased a Naim Supercap for several thousand dollars last month F&F. It’s certainly not for everyone, but to believe that there are not a ton of transactions happening this way is simply uninformed thinking.
There are also some great dealers of used gear for the risk averse, TMR and ECHO are both excellent.