I think the problem is in the name second "life"... everyone knows life begins at 40... maybe it takes a minimum of 40 hours to become at least basically acquainted with the way the viewer works, how to interact etc.

Someone pops on to see what it's like... but they don't see anything. They can't make an opinion without devoting a huge amount of time to really find out. By that time the decision is made for them and they love it. Or the decision was made much earlier and they become impatient , give up, run out of their fixed amount of leisure time and leave.

Time is definitely the factor here. There is no demo version, you can't get an overview as there is so much to do or see... yet visibly so very little.

I explored for days, talking, trying, discovering, exploring... I was lucky, I had the time to do so. All user are experiences are different. There is no catch all and there can therefore be no linear route to your Second Life. Determination, Fascination, Exploration, Intimidation, Derision... all words to describe a person's motivation for either staying or leaving... but only if they have the time.