Actually , we consider the direction of +ve charges flowing in an direction ,
Suppose +ve charge is flowing , rightwards so the direction of current will also be in the rightwards direction .
Now , let consider -ve charge is flowing say electrons , suppose they are flowing in rightwards direction , so the direction of current will be in rightwards direction ? The answer is no ! , because for the flow of electrons they need some potential difference & move towards +ve one , so if the electrons are flowing Rightwards so +ve charge will be flowing in the leftward direction .
You can also understand with the example of a battery , we always take current coming out from the +ve terminal of the battery , current move from high potential to low potential , i.e. from +ve to -ve , & electrons move from -ve to +ve (low potential to high potential )
• If we take flow of electrons as current , the we have to take the value of current as always -ve , but for sake of simplicity we take or consider the flow of +ve charges , for a +ve magnitude & calculations ,
• So , always consider flow of +ve charges as current in short ,