When you venture into "people should change their mentality" logic you are likely to meet with disappointment. I am saying this with utmost respect for your thought process though. The very reason it is a common mentality is because "it works so far".
> this is a very specific Indian thing which I cannot begin to understand as there are already less women than men.
It is because parents just don't want to get rid of the daughter. They want to use her as a currency to get related to a much richer family than them. That is what makes it a far tougher market.
Think of it like this. You might think you get more sex as 20 year old because of your youth. But in reality a 20 year old is likely to sleep with girls between 18 to 20 year old. But if you are 40 year old your target set becomes 20 to 35 which is much bigger and very likely you might get more sex partners than 20 year old.
If you are a girl with income level X you want a husband whose income level is 2X. The boy can chose any girl from income levels < 2X. In fact higher up you are on economic level you can point your finger to a girl and pick her to marry.
The single "I am not getting a wife" people are essentially at the poorer spectrum they are not uniformly distributed. These are the people sending "show bobs and vegene" messages on facebook !