There are friends who take advantage of people. E.g., getting a free ride or free lunch. If it was a fair deal, they should take turns unless of course they are in a dire strait situation. For those who cannot afford it, they should be honest about it and tell those who are their friends of their difficulty rather than take things for granted. I once had a friend who would only call me when she needed to buy some stuff from the place I work just to enjoy my staff benefit of getting discounts.
There are those who make use of people, just to obtain information. They are great manipulators. I had a friend in top management who did just that not only to me but to many others. This person is supposed to be a leader by example.
There are those who just call when they want to make a business transaction. For example, my insurance agent friend. Once there is no hope of a transaction, the relationship is off.
Of course, there are true friends but they are hard to come by.
I do not mean to sound negative or judgmental, but people often have reasons for being friendly. There is very little sincerity these days. It is sad that true friendship is so hard to come by.