I think big businesses benefit from donating to any type of charity, period. They are showing the public, which is full of potential investors, customers, and employees, that they care about something more than their own profits. They are helping better the world by donating something that they can afford to part with. A charity that helps the poor get back on their feet has the added bonus that the business is directly helping people better their lives.
Contributing to charities that make quality of life upgrades available, even to the poorest of people, would likely make those people more productive, healthier and longer lived. The more money and better quality of life the poorest people have, the more money can be spent on the things those companies offer.
When poor people become able to participate in the global economy, they remain loyal to brand names and companies that helped them have a better life. I saw this, myself, in South Korea. To this day, Sanka is the coffee of choice there. Some was donated during the initial conflict. Even when donating products and services that a company doesn't sell, this same benefit could be had. By associating their company with the support of a charity, generations of loyalty could be established. These types of humanitarian gestures aren't lost on consumers of influence, either. Even with minimal publicity, consumers often become aware of charitable donations by large companies. I know people who shop on the basis of how giving large businesses are.
Big businesses that give to charities that help make quality of life upgrades affordable to the poor can benefit by these actions. I believe that they can use that to help with their public image, and in the big world of public opinion. It also sets an example for others to follow, and sets them as leaders with heart and compassion for others. It is also a nice tax break, and large companies are always looking for a tax break.
Many large businesses and corporations donate to charities to help the poor. This is because these businesses also receive a benefit in the form of good public relations. People, for example, may go out of their way to do business with a corporation they see as also helping out the poor. In addition, by donating to the poor the businesses reduce the need for government to provide assistance, which is usually paid for by taxes that can hurt business.
Many big businesses lose all concept of relationship. Individuals become dollars and they lose a relational level, but at this point big businesses are not helpless to gain back a feeling of relationship with individuals. Contributions such as the one mentioned here can be a great way to secure again a relational connection with individuals, communities, etc.
While charitable work should never be done with an ulterior motive, this type of charitable behavior would likely pay dividends for big business. If they are helping to reach down and pull people out of the slums, then those people are likely, in turn, to be able to consume things that these big businesses create for their consumption to a much larger degree. In this scenario, everyone wins.
In purely financial terms, big business can make charitable donations which can then be written off against their taxes. It makes them appear "human", and would help create a positive image for the company. On a wider scale, by contributing to charities and improving the quality of life, everyone benefits in the long run when people become better off and better educated. There is a parallel with the philanthropic industrialists of the industrial revolution who believed that providing amenities for their workers would make them happier, and therefore improve productivity.
It has been shown that when someone (in this case, a business) does something good for the less fortunate, it is returned to them tenfold. The Bible even tells us that doing good for others will be returned to us 100 fold. We are also taught to help the "least of our brethren". Treat those as we would want to be treated.
If a person or a family is worried about how they will be able to eat their next meal or where they will sleep that night, they will not have the money that is necessary to purchase items that are not completely necessary. If big businesses relieve some of that pressure they would create a customer who would be loyal to them because of their help and a customer who would have more of the funds needed to purchase items that are not completely necessary for life.
Big businesses would not benefit from contributing to charities that make quality of life upgrades for the poorest people in the world. This is because most of the poorest people in the world are located in places that have poor infrastructures and policing. This makes these places dangerous for a company to come in and sell goods because nobody can afford them and theft is rampant.