I had an e-mail from a JW (fading) contact. He said that their CO said to him, that it was because after they had settled child abuse cases in USA. They had found that if a WT authorised meeting was held in a persons home and something happened, then the WT could be held responsible.

Whether this is true or not we can't be sure, knowing how JWs come up with all sorts of reasons for things.
But its an interesting one.

"Only in a world where faith is difficult, can faith exist"