This is actually the second time the Raptors have won the draft lottery.
They won in 1996, but one of the conditions of their expansion franchise was that they couldn't have the #1 overall pick during their first three years. Philadelphia picked first and took Allen Iverson. The Raptors picked second, and selected Marcus Camby.
The other owners insisted on this clause because the Orlando Magic had had the #1 pick in two consecutive drafts, (1992 Shaquille O'Neill; 1993 Chris Webber), and played in the NBA finals in 1995. They didn't want a Canadian team to do the same.
The Raptors and Vancouver Grizzlies also only had the 7th and eighth picks in their first draft, 1995. In the most recent expansion, (2004), the Charlotte Bobcats were given the #2 pick.