Mainoo has been linked with an Old Trafford exit in January, partly to help the club's PSR concerns, with Chelsea rumoured to be on the verge of bidding for the teenage sensation.
But Parker has told sweepstakes24.com, that he can't see why the midfielder would leave his old club unless he's getting some questionable advice.
"I think the only way that it would go that way is if Kobbie is being advised badly or being silly and asking for too much money," Parker said.
"Maybe an agent who is using what he has done in such a short space of time, saying to grab it now."
"Football is short and I get that, but he’s still very young and at the biggest club in the world, so why look to grab the money now when over the long-term he has everything ahead of him. He just has to look at so many other players that are still doing well now, who have stopped playing a few years ago."
Mainoo made his first team breakthrough last season, quickly establishing himself as one of United's key players and forcing his way into England's Euro 2024 squad, and Parker can't see, as a local lad, why he'd give up his current standing in Manchester for fighting for a place at Stamford Bridge.
Adding: "To be leaving Manchester United and going to Chelsea, and you look at the number of players that they’ve got already around his age in midfield on £200/week, Chelsea will have to justify those players by playing them.Getty
"I can’t really believe that a boy from Stockport is going to want to give up everything, playing for a club he supports, playing regularly at this moment in time, that he’s going to walk away to play for Chelsea.
"Even though Chelsea are doing better than Man United at this moment, whatever he does at Chelsea would never mean as much as doing it at United, so why give it up?
"I look at how he plays with Ugarte and I have just seen too much in there for United. It goes against everything that United is built on, that when young players progress, they don’t suddenly get rid of them and sell them straight away unless they want to move on, like Beckham to Madrid."
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