We don't know why neither, but Vollee is now offering Second Life Mobile open beta for 40 Wi-Fi-enabled and 3G cell phones, and it will support more mobile phones soon, say your iPhone2.
Vollee says:
"Second Life Mobile is a thin client downloaded to the high-end cell phone that communicates with the full, unmodified game that's hosted on Vollee's servers."
More info:
Vollee>>Second Life
[via Download Blog]