During the peak shifting season (March to September), many genuine packers and movers in India request a down payment as they are in high demand during the peak time. The advance money being paid to the service providers more or less acts as insurance that if you cancel the agreement with them, then they will have some sort of compensation and do not suffer from any loss.
It is not uncommon for most of the shifting companies in India to ask for a certain percentage of down payment.
However, it is also important to note that not all the service providers request for advance money, it largely depends upon company to company.
If we look into the law, if a packers and movers company has a rule of taking money in advance, then it must state it clearly in its terms and conditions.