That runs into the problem of incentivizing various poison-pill type strategies to make it expensive in other ways to accept the standing offer to sell. Like, a high-level mobster could easily list their properties well below market rate while letting it be known to potential buyers that actually trying to purchase the property means saying goodbye to your kneecaps.
There's a similar corruption issue on the government-sets-buy-price side, where unscrupulous officials can transfer wealth to individuals, but at least the corruption there is much more able to be audited.
