Their success rate at conversions is abysmal. Their success rate at getting inactives back in is slightly better. It's just a numbers game.
I had a JW who used to be a neighbor of mine stop by with an elder to invite me to the "special talk" a month or so ago. He's a genuine old guy but the comment earlier in this thread about taking advantage of the less educated reminded me of that visit. Neither the former neighbor or the elder are particularly deep thinkers. He had just run into my parents a week or two earlier at some event and it reminded him he hadn't seen me in five years. I actually felt bad for them for wasting their time with me and wasting their lives in a cult.
I guess my point is, they're going to have to make it somewhat easier to return (for inactives, not apostates) if they don't want their growth numbers to keep shrinking.