A partner may have some particular responsibility or extra task that others have not got. It may in fact be of a temporary nature. To compensate him for this, it is best not to disturb the profit and loss sharing ratio. It is better to let him have a salary sufficient to compensate him for the extra tasks performed.
This salary is deductible before arriving at the balance of profit to be shared in the profit sharing ratio. A change in the profit and loss sharing ratio to compensate him would have meant bearing a larger share of any loss, hardly a fair means of compensation; or if there was only a small profit, the extra amount received by him would be insufficient compensation, while if there was a large profit he may well be more than adequately compensated.