In the beginning of Chapter 5 in The Great Gatsby why did Gatsby have all the lights on?

In The Great Gatsby, Gatsby tells
Nick all of the lights are on in his mansion because he's been "glancing into some of
the rooms." 

From a distance in his taxi, Nick at first
thinks there must be a fire.  Then when he sees that the brightness is coming from
Gatsby's house he assumes there's a party going on.  When that turns out not to be the
case, and Gatsby says he was just glancing into the rooms, Nick appears unsure of what
to think.

The suggestion is, I believe, that the lights are
all on so that Gatsby's house can be seen from Daisy's house.  This is a reversal of
Gatsby staring at the light on Daisy's dock.  This is wishful thinking on Gatsby's part,
of course--Daisy certainly isn't staring at his house from across the
water.

There may also be a sense that Gatsby is inspecting
the home in order to prepare for Daisy's eventual visit.  Remember that one of the first
things he does with Daisy once they do meet again, is to give her a tour of the
house.