Uncapped Maddison, who has been in fine form with Leicester this season, was sent home from the October game in the Czech Republic due to illness but was then spotted in a casino while England were losing the match.
Southgate said there was no question of Maddison having asked to go home, but said that he was unwise to have visited the casino.
“We sent him home – he was ill. It wasn’t right for him to travel with the rest of the group,” said the England manager.
“So any suggestion he chose to go home because he wanted to go out is unfair. It’s not a great decision he took (to visit a casino).
“As an England player you have a different profile. Everyone has a camera-phone and know they can make money selling pictures. We are supporting him because we picked him. He has to fight for a place like everyone else.”
Manchester City central defender John Stones returns to the squad at the expense of Everton’s Michael Keane, who struggled in Prague.
There was no call-up again for Manchester City right back Kyle Walker with Southgate sticking with Liverpool’s Trent Alexander-Arnold and Atletico Madrid’s Kieran Trippier in that role.
Yet the England boss rejected the suggestion that the 29-year-old Walker’s national team days were over.
“Absolutely not. We’ve been very pleased with the form of Kieran and Trent, whose form for Liverpool has been really exceptional. It’s an area of the pitch where we’ve got high competition for places,” he said.
Midfielders Jesse Lingard of Manchester United and Dele Alli of Tottenham Hotspur also failed to regain their spots in the squad after spells of injuries and poor form.
But Liverpool midfielder Alex Oxlade-Chamberlain, who has been featuring more regularly for Juergen Klopp’s side after recovering from a long-term injury, did earn a recall.
Uncapped Aston Villa midfielder Jack Grealish, who had been tipped by some pundits for a call-up, remains on Southgate’s radar with the manager saying he might yet be brought in if there are injuries over the weekend’s Premier League games.
England face Montenegro at Wembley next Thursday in the country’s 1000th international fixture, before playing away to Kosovo on Nov. 17.
Southgate’s side need to just pick up a point from their remaining games to secure their place in next year’s finals.