Yeah, but the poor people are the one who is badly in need of more incoming validity. Rich and even middle-class people don't need extra validity as they mostly queue their plans in advance. Even if they forgot to queue, they will surely do a recharge when they found outgoing is blocked, but not a big hassle for them, since incoming will be working before their recharge. But Poor people usually will wait to recharge till the completion of the (or at least the last day of) incoming validity. Now they are forced to recharge minimum once a month.
Earlier poor people can recharge just 10.5 times a year (28+7days = 35 days; 10.43 recharges per 365 days). Now they have to recharge 11.8 times a year. Almost 2 more extra recharges a year.
Here we have to understand the greedy & cunning nature of Airtel. 28 days + 3 days = 31 days = One Calendar month. If some poor person recharges his number on the salary day, his incoming validity will end exactly on the salary date of next month, when he mostly will have money. This will hold true for 2 days incoming validity (28+2 days) as well, which will be their next logical step, imho. I mean they may reduce the 3 days extra incoming validity to 2 days, if they get no backlash for this change.
It is logical for poor people with multiple SIMs to dispose all other SIMs except their primary number. Even this is a problem for middle class people, for whom 2 SIMs is a must, due to coverage difference (in home and work place). For them BSNL is the only upcoming "White Knight" and NOT VoId. VoId is more like a "Shadow of Airtel".