Cultural sensitivity, rather than athletic logistics, motivated the shift. The International Volleyball Federation explained that not all countries or cultures are comfortable with the amount of long-and-lean skin on display during the beach volleyball matches. A spokesman said, "Many of these countries have religious and cultural requirements, so the uniform needed to be more flexible," although the countries wanting the change were not specified. Beach volleyball has only been an Olympic sport since 1996, and the new rule is meant to encourage more countries to compete.
It's pretty crazy the sport previously mandated that the women wear such a revealing uniform, since more coverage obviously doesn't have an impact on how the men play. Could it be that the idea of women bending, stretching, and jumping in bathing suits is considered a draw for viewership? Either way, it's expected that most players will wear the typical sports bra/bikini bottom ensemble at this year's Olympics.