An indian wedding is not just "a wedding" -- it's a huge social event that defines the social standing of a family in their community. A successful wedding will result in increased respect and trust for family members, which will likely have a direct economic impact: people will be more likely to lend you money at a favourable rate, they will entrust you with responsibilities and money (i.e. good jobs) and so on. It's also a great occasion for networking per se. In many rural communities, not just in India, wedding ceremonies are often an investment, not a cost. Think of it as a huge PR event where people are basically forced to attend (not attending a wedding of somebody you know, after being invited, is very disrespectful) and where you can sell them stuff while they enjoy themselves.

A huge dowry, now that is a waste of money, but it's not mentioned in the article.