Why does a company's profit appear as a credit on its balance sheet?

The accounting equation and the double entry system provide an explanation why a company's profit appears as a credit on its balance sheet.Asset accounts usually have debit balances while liabilities and owner's or stockholders' equity usually have credit balances. When a company provides services for cash, its asset Cash is increased by a debit and its owner's equity is increased by a credit. The credit is initially recorded in a revenue account, but revenue accounts are temporary accounts that cause owner's equity to increase.If the owner withdraws some cash for personal use, the asset Cash will decrease through a credit and the owner's equity will decrease through the debit part of the accounting entry. The debit might initially be recorded in the sole proprietor's Drawing account but this account is also a temporary account that will cause the owner's equity to decrease.Generally speaking, the credit balance reported in the owner's or stockholders' equity section of the balance sheet reflects the owners' investments in the company plus the profits earned minus the amounts distributed to the owners since the time that the company began.

Net profit appear in the Equity section on the balance sheet based on The Economic(Business) Entity Concept whereas the owners of the company considers another party and they own this profit which came from taking the investment risk.

I have some conservation about the word "credit" the balace sheet is A statement NOT an account. 

(It is assumed that readers have the knowledge of Debit / Credit rules and normal account balances.)

See the accounting equation...

Assets            =           Liabilities + Owners' equity

Now consider the following different forms of this equation;

Debits            =            Credits

Assets            =            Claims (on those assets)

Assets            =            Outsiders' claims + Owners' claims

An example of outsiders' claim is funds provided by them (loan) and return thereon (interest).

An example of owners' claim is funds provided / invested by them and return thereon (profit)

As far as "claims" (loan, interest, investment, profit) remain in the business, they appear on one side (credit side) of the statement with corresponding assets (e.g cash) on the other side (the debit side).

(Please note that discharged claims such as repaid loan, paid interest, divestment / drawings, profits distributed, do NOT appear on the balance sheet as the act of discharging claims has reduced the assets on the other side. e.g CASH payment)

First of all, in your question there is small correction required. For Balance Sheet there is no credit or debit since it is not an account. Its only a statement which shows assests and liablities on a specific point of time arranged in a particular manner. J

Here we can start from the Business entity concept. As per this concept business entity is entirely different from its owners by existence. Suppose business is person ‘A’ and Owner is Person ‘B’.  Person A’ is owed to person B for the investment of B’s capital. Since this is a long term commitment/ obligation.

Profit is the reward of risk taking. And of course it is the reward for its investor. Any accrued liabilities or incomes is there while winding up a business these all paid off from the capital. (remind the accounting equation Assets – Liabilities = Capital). In short all the payments write-offs or any other receivable will increase or decrease capital. And this is the reason the profit showing along with capital and having credit balance.

Profit and/or loss defined as the change in equity, so profit is Equity by definition ( It belongs to Owners or Shareholders and not belongs to Debtors or Employees), Profit and/or Loss is the increase and/or decrease in Equity resulted from the operation os Assets through a certain interval of time.

Assets Not necessarily belong to Owners only as (it may be financed by debt = Liabilities ).

Because profit is part of equity and equity has credit nature

As per the Separate business entity concept  i thing u r question wrong usually balance sheet  as of date what we have receive and what we have to pay so Company profit need to pay the owner, that's what we showed under balance sheet liablity section

owner of the business we treat as a separate person or need to pay whatever he invested in the business and whatever he gained in the business and whateve losses in the business