Many of our creatives are leaving the community for other platforms, and regular players leaving as it feels like growth has stagnated too long. With the age of the game it is getting more and more rare for people to stumble into secondlife and stay.
Bringing the game back to steam will give a trusted platform for people to discover the game through, and while buying linden through steam might not be as profitable having to cut in another platform, but if it is done right it could at least bring in new players and help them migrate to the off steam downloads.
Steam has changed a lot since last SL was on it, now featuring games with adult content, SL is tame by most comparisons.