United forked out £40m to sign the 23-year-old from the Dutch champions this summer but he is yet to start a Premier League game.
The likes of Paul Pogba, Fred, Scott McTominay and Nemanja Matic have been preferred to Van de Beek in the opening weekends of the campaign.
Van de Beek was an unused substitute when Manchester United drew goalless with Chelsea in the Premier League on Saturday.
"We’re talking about Van de Beek, nothing against the kid, but why have we bought him? He’s watching the game from the stand every game," Evra said via Sky Sports. "We don’t need him, that’s the truth."
Neville added: "What is a little bit of a mystery is the use of Van de Beek since he’s been signed for £40 million."
"He doesn’t seem to be at the forefront of Ole Gunnar Solskjaer’s plans in every game. It’s a bit of a mystery that one. And the more he doesn’t start, and the more he doesn’t come on, the more you’re thinking, 'Well £40m player, ordinarily you’d get him in the team'.
"He must be thinking: 'What am I doing here?' at this moment in time."
Solskjaer however maintains Van de Beek will get his chance as the season progresses, with the games coming thick and fast at this point in time.
"Don't worry about that. He'll get his games. Don't worry about that," Solskjaer told Sky Sports. "It's easy to say who should be playing and more difficult to say who shouldn't."
United host Bundesliga side RB Leipzig in the Champions League on Wednesday.