Many Buddhist peoples have developed the idea that to help their fortunes and to get a better rebirth, they will give hoping for a greater reward in the here and now or upon their next rebirth. It is a karmic savings account so to speak, earning interest for the next life or better circumstances in the current. I have not seen this as much with western converts, but it is very common with cultural Buddhists and people who grew up in Buddhism.

It takes many forms, whether giving in monetary form, giving of their time, providing the four requisites for monastics (clothing, shelter, medicine, food), driving monastics places, and many other things. According to Buddhism, the acts of generosity should be given without expectation of some reward. It hinges upon intention, which matters a great deal with actions one does. Intention is what often separates a Buddhist interpretation of karma/kamma from that of a Jain as well (especially in regards to killing/harming). You will see some of the monastics in places like Myanmar/Burma try to clear their minds when they do some aspect of genicide or inciting hate towards different minorities in their country. There is still the intention there to clear the mind to commit wrongful acts.

An excerpt from a Buddhist sutta on the matter of giving with expectations of reward:

[…] “Having given this gift seeking his own profit — with a mind attached [to the reward], seeking to store up for himself, [with the thought], ‘I’ll enjoy this after death’ — on the break-up of the body, after death, he reappears in the company of the Four Great Kings. Then, having exhausted that action, that power, that status, that sovereignty, he is a returner, coming back to this world. […]

[…] “This, Sariputta, is the cause, this is the reason, why a person gives a gift of a certain sort and it does not bear great fruit or great benefit” […]

Source: Dana Sutta: Giving (AN 7.49)

Offsite Resources: No Strings Attached: The Buddha’s Culture of Generosity by Thanissaro Bhikkhu