The Supreme Court’s declaration that same-sex marriage was constitutional triggered widespread jubilation across the United States on Friday, as millions of people took to Facebook, Twitter, and Instagram to show their support. This enthusiasm was matched by numerous brands, such as Chipotle and Target, who used cleverly produced tweets to trumpet their position on Twitter.

The response from the country’s sports teams, by contrast, were relatively muted. Of the 122 teams in the four major American professional sports leagues—the NFL, NBA, MLB, and NHL—only five explicitly mentioned Friday’s ruling as of 7:30 pm Eastern time last night. Three—baseball’s San Francisco Giants, football’s San Francisco 49ers, and basketball’s Golden State Warriors—hail from the famously progressive Bay Area, while the other two (the NBA’s Los Angeles Clippers and Sacramento Kings) play elsewhere in blue-state California.

In fairness, social media isn’t the only arena in which sports teams interact with their community, and several have expressed support for gay rights in other ways. The Seattle Mariners, for example, will fly a rainbow flag during their game against the Chicago Cubs on Sunday. But the silence of so many teams on Friday was nonetheless striking. Why is the professional sports world so slow to embrace a social change favored by a large majority of Americans?

Homophobia in sports has deep roots. In the 1980s, the Los Angeles Dodgers reportedly offered Glenn Burke, a player widely believed to be gay, $75,000 to marry a woman. Two decades later, the retired NBA player John Amaechi described rampant homophobia among his former teammates and the relative indifference of league authorities. Even in the absence of traditional gay bashing, players encounter an extremely heteronormative environment when entering the world of professional sports. At the NFL Combine in Indianapolis, a venue for prospective amateur players to try out in front of professional executives and scouts, teams reportedly asked the players whether they were married or had a girlfriend.

“Professional sports teams still haven’t been able to shake that toxic culture of masculinity,” said Dave Zirin, a journalist who specializes in the intersection of sports and progressive politics. “It’s still something that dominates the industry in a much more intense way than executives would like to admit.”

Will American sports eventually embrace gay equality? According to Zirin, leadership is unlikely to come from the top. “It’d certainly be welcome if a commissioner were to come out strongly in favor of same-sex marriage,” he said. “But doing so would put their bosses—the league owners—on the spot. That might prove polarizing at the next owner’s meeting.”

A likelier driver of change may be the players. When Jason Collins became the first active NBA player to announce his homosexuality in 2013, stars like Kobe Bryant and Dwayne Wade tweeted out their support. But Collins—who has since retired—remains a singular figure, and the prediction that his coming out would lead to several others has not yet come true. The beliefs of players like Minnesota Vikings cornerback Josh Robinson, who on Friday compared same-sex marriage to pedophilia, no doubt contribute to the reluctance of closeted players to announce that they are gay.

Instead, Zirin believes that change is likely to occur not through executive fiat but rather a persistent, under-the-radar effort.

“People forget that professional sports are social institutions, and that social institutions change when people organize on a granular, grassroots level within those institutions,” he said.