"There is a great difference between 31
inches of pitch though it may not sound of much!"
Hey, I don't find too much difference between 31" & 31"!
Typically, 'healthy' airlines operate with 75% load factors - if it's too high, it means that you're leaving pax behind at peak periods, and obviously if it's too low, you're not filling your planes up.
So, when you consider that the increased seating capacity would allow for more pax during peak "full" flights, there is some business sense in it. It's a very easy to way to reduce seat mile costs too.
As a passenger, I'm not going to laud such plans though.