In chapter 8
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Gatsby is so busy with Daisy now and he no longer needs to impress her (their affair is implied) that he no longer needs to keep up his house. He has won her over and doesn't need to throw large parties to try to lure her to his house.
He is also trying to maintain her reputation. As a married woman it would be inappropriate for her to be at his house and maids, housekeepers or butlers would be likely to talk to other maids housekeepers or butlers thus letting it out that Daisy and Gatsby were having an affair. This would ruin Daisy's reputation.
The Great Gatsby, Fitzgerald