Should the investment securities that companies own be left on the books at historical cost, or should

Question:

Should the investment securities that companies own be left on the books at historical cost, or should they be adjusted annually to their current market price (as is now required by GAAP)?
When physical assets are purchased, they are recorded on the at cost and left there until the asset is sold. For example, when land is purchased, the cost of the land is recorded on the books. If the land increases in value, no adjustment is made. The company realizes the gain in value when it sells the land at a gain. Why don’t we do this for investment securities? Why should the assets for land and securities be handled differently?

Balance Sheet
Balance sheet is a statement of the financial position of a business that list all the assets, liabilities, and owner’s equity and shareholder’s equity at a particular point of time. A balance sheet is also called as a “statement of financial...