Why Indian Telecom Operators Have 28 Days Validity?

In India, prepaid mobile plans have a validity of 28 days only, not of 30 days there are many telecom operators in India like Jio, Airtel, Idea, etc, and they offer almost similar plans.

They're trying to increase revenue and increase profit through incremental creep. They are hoping people won't notice and will just pay. The actual thing is if they will offer for 30 days and not for 28 days then they will not be able to increase profit. If they will offer only 28 days, then the customer will have to recharge 13 times in a year and it will increase their revenue because no one is questioning them. They are doing what they want and the customers are suffering the charges.

However, the BBC report, citing a UK-based price comparison site said that 1 gigabyte (GB) of mobile data costs in India is approx. $0.26, compared with approx. $12 in the US and approx. $6 in the UK. The global average price is approx $8. In India, the average mobile data consumption is 10 times in 2 years, to more than 10 GB per user per month, it is roughly the same as in the USA.