The loss of Haines from movies is the gain of interior designers even today. The man was enormously influential in creating the California Casual style of modern decorating. Haines mixed and matched very modern pieces with antiques and ushered in the age of informal entertaining. The way you think about organizing social areas in your home and even how it's laid out are influenced by Haines.
Haines decorated the homes of many big stars and Hollywood moguls. One of his first jobs after getting fired by MGM was decorating the home of Fox's CEO! Talk about payback! Haines then went on to having huge spreads in fan magazines like Photoplay and Life. These spreads of stars' homes influenced readers all over the country and they began to imitate the stars' style of living. By the 50s, Haines had made the American style the most influential interior design style in the country. Prior to that, people were looking to English country house, Bauhaus, and (in California and the southwest) Spanish. The house of Norma Desmond in Sunset Boulevard is a great example of old Hollywood Spanish style. It's comfortable but stiff and fussy. Haines ditched all that for a newer, sleeker, and more casual style that looked elegant while complementing the flowing and open spaces of more modern houses.
He was a fascinating man and I too want to read his biography.