“With the exception of Christmas and Easter, Southern Baptist congregations in America generally do not observe the days of the Western church calendar. Instead, they tend to follow the pattern of the Puritans, who believed following the liturgical calendar violated their liberty of conscience (many Puritans refused to celebrate any holidays besides the Lord’s Day). Some Baptist churches, however, have begun to incorporate Advent observance in their preparations for Christmas.” — Southern Baptists and Advent: Four things to know
Based on my own experience, not with the Southern Baptists but with a different church that did not use the liturgical calendar, I would have thought they did not observe advent because a) what’s Advent? b) we didn’t do that last year; and c) that’s something Catholics do. It’s kind of refreshing that it’s because advent was something the Church of England did, and that the Puritans resented having been forced as children to go to Advent services.