In the US it’s contingent on some quirks of gambling law. Dedicated online sports gambling was broadly legalized in most states a few years before sports came to prediction markets (during the early days of prediction market discourse, online sports betting was mostly banned anyway by a federal law struck down by SCOTUS in 2018). But prediction markets are less regulated than the sportsbooks, e.g. they have an minimum age of 18 while sportsbooks are 21 in most states. Otherwise sports markets on prediction platforms would presumably mostly just displace gambling elsewhere.
In the US it’s contingent on some quirks of gambling law. Dedicated online sports gambling was broadly legalized in most states a few years before sports came to prediction markets (during the early days of prediction market discourse, online sports betting was mostly banned anyway by a federal law struck down by SCOTUS in 2018). But prediction markets are less regulated than the sportsbooks, e.g. they have an minimum age of 18 while sportsbooks are 21 in most states. Otherwise sports markets on prediction platforms would presumably mostly just displace gambling elsewhere.