I will assume that the plant assets' liquidation values are higher than the present carrying values when answering your question.
Plant assets (buildings and equipment used in manufacturing; also called fixed assets) are not reported at their higher liquidation value because of several accounting principles. Below are four accounting principles that come to mind.
The cost principle requires that plant assets be reported at amounts that are not greater than cost. Cost is an objective and verifiable amount. Liquidation value is subjective and the amount can vary significantly depending on the assumptions made.
The matching principle requires that the cost of plant assets be allocated to depreciation expense. This means that over a plant asset's useful life some of the plant asset cost is matched with revenues on the income statement. Therefore the plant asset's carrying amount will be decreasing each period.
The going concern assumption implies that the company will be continuing in business. Since it is assumed that the company is not liquidating, the liquidation value of the plant assets is not relevant.
The revenue recognition principle prohibits a company from showing a gain from merely holding a plant asset. What would you credit if you increased the plant asset amount?
Those four accounting principles provide some of the rationale for not reporting the liquidation value when it is higher than cost.
If a company is not a going concern or if the plant asset's value has been impaired, the above rationale does not hold. For those situations you will need to follow the appropriate accounting rules.