The Hurricanes will now be led by veteran hooker Andrew Hore after So’oialo was in charge for 49 matches after taking over from Tana Umaga in 2006.
The All Black flanker said he wanted to concentrate on his playing ahead of the World Cup.
"I want to really concentrate on my preparation and to be the best I can at what I do," he told The Dominion Post.
"I want to offer the Hurricanes and the franchise the best I have and to do that I need to really focus on getting my body right.
"It was tough, but then again you have to make these decisions to benefit the team and yourself really."
The 62-Test veteran was replaced by Kieran Read as the All Blacks' Test No 8 during last year's end-of-year tour - a move that has clearly irked So’oialo.
"It's an investment really – for the future," he said.
"I want to try and continue to contribute my all to the Hurricanes and to the All Blacks for the next two years."
It will also be the first senior side that Hore captained in his long career as a player.
"I captained the Otago development side for a bit, but nothing too serious really," he said.
"But I've been in a few leadership groups as well though and there's a lot of the same guys around here too. It's going to be huge, I'm looking forward to it.
"Hopefully, my game grows from it.
"I'll just try to say it how I saw it and get going from there. There won't be any poetry coming out of me."
"I did expect him to carry on, but it's a mark of the man really that he's done what he thinks is best for the team," he said.
"We had a yak with the leaders and the senior players about a week ago and came up with a few ideas.
"I've been here for a while, but I'm coming to training with a bit more on my mind, which gets you thinking and I think that's quite good for me as well."
Hore will lead the team in their pre-season game against the Brumbies on Friday.