One of the biggest obstacles to friendships is distance. This is reduced by the Internet. However, another limit is time. Some may only be able to make brief contacts and not be free to move from the acquaintance to the friend category.
Also people can be fluid as their circumstances change. For example, a gal may find her friends do not have as much time for her when they get married.
It may be a good idea to invest in and receive whatever level of contact comes along. If brief, then welcome whatever exchange occurs with the time available. Close deep and lasting friendships are rare and all the more precious because of it. However, there are all sorts of other relationships that also have value.