I suppose online casino's don't have the same lure that land based one's do to tempt you to pour some more cash in on your walk away from the cashiers cage.. I mean, it's a lot easier to click the 'X' button in the corner of your window than stroll past a big line of slots
Still, it's a bit of a poor show.
I hate to say it, but Jackpot Factory had the right idea when I used to play there. They gave me a no strings bit of cash in my account when I made a large withdrawal to say "congratulations". That made sure I logged back in and played - and subsequently ended up depositing.
It's not rocket science.