In India, appliances are 220 volts enabled. However, many Electricity Boards often provide mains power at less than 220 volts. What are the possible reasons?

Is it because of technical inefficiency? On the consumer end, if the "actual load" is higher than the "connected load" (as shown by the Electricity Board in the power consumption bill), can the input voltage appear low in the voltage regulator?

Any decrease in the voltage feed is caused by a voltage drop in the feed woire or feeding transfomer. And you are correct, any load will affect the vpltafe tested at the source with the load attached.