I've never quite understood how pensions are supposed to work when one changes jobs every 1-5 years. With 401(k) I can roll my account into a Vanguard IRA and k

I've never quite understood how pensions are supposed to work when one changes jobs every 1-5 years. With 401(k) I can roll my account into a Vanguard IRA and keep all the control. I'd hate for my retirement to be beholden to 5-10 different sets of pension fund managers.