Why Transfer function doesn't check for allowance comparing to TransferFrom?

Question

1. Why Transfer function doesn't check for allowance comparing to TransferFrom?
2. Do I need to call increaseAllowance each time before calling TransferFrom?

Ex implementation of Transfer without allowance check

    function transfer(address receiver, uint256 numTokens) public override returns (bool) {
        require(numTokens <= balances[msg.sender]);
        balances[msg.sender] = balances[msg.sender].sub(numTokens);
        balances[receiver] = balances[receiver].add(numTokens);
        emit Transfer(msg.sender, receiver, numTokens);
        return true;
    }

Answer 1

1. Using account A in order to execute transferFrom(source, target, amount) requires both:
   • source holds at least amount of the given token
   • A has been approved by source to transfer from it at least amount of the given token
2. Using account A in order to execute transfer(target, amount) requires only:
   • A holds at least amount of the given token
3. Your question is essentially, why doesn't it also require:
   • A has been approved by A to transfer from it at least amount of the given token?
4. And the answer is obviously:
   • Because it is pointless to approve yourself to do something (anything really)

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This is true regardless of whether A is an externally-owned account or a smart-contract account.