Altruism has an evolutionary basis. You are driven to propagate your genes, so taking actions to benefit the life and survival of several of your children, or a greater number of your nieces and nephews, is advantageous to your genes. A step further and it benefits your community or society, and builds bonds between people who need to work together to survive.
Sometimes you will do this consciously, as when you dive into the river to save your own (or others) children at the expense of your own life.
But a lot of the time, it is unconscious behaviour, so your altruistic drive tends to be spread more widely, and expressed in supporting causes that help others, whether they share your genes or not. And, because you are not necessarily doing this consciously, you get rewarded by the release of feel-good hormones, such as endorphins, dopamine and serotonin. Sex is also essential in order to pass on your genes, but people do it because it makes them feel good - those hormones again (otherwise it's just pretty messy).
So, yes, superficially people are altruistic so that they can feel good, and you can argue that some examples of altruism are a bit silly. But that doesn't mean altruism generally is to be sneered at. It may be the single most important thing in the evolution and development of human society.
Why do banks do it? 1) They are made up of human beings, who tend to behave altruistically. 2) Even if they are run by non-altruistic psychopaths, the latter succeed because they realise other humans are motivated by and respect altruism, so it's to their selfish advantage to appear altruistic. (That's bypassing the issue of what banks do as part of our economic system - they help us avoid having to grow a whole lot of veggies and chooks to trade for a house).

I can't remember having ever questioned acts of altruism.
I've merely accepted them - whether the altruism came
from people who were in a financial position to help others
and from ordinary folk. I thought it was just great that they
were doing some good without questioning their motives.
I felt that what mattered was that good was achieved and their
reasons for doing it - did not really matter in the overall
scheme of things.

At the end of the day surely if we can help ease another's
pain - that's what matters. And shouldn't our lives involve
at least some - acts of kindness and compassion?

Personally, I believe most of us (if we can manage it) engage in a limited amount of altruism or supporting a Charity of some sort. Obviously it depends essentially on the amount of income most of us have remaining, at the end of each fortnight. Of course with rising prices, and the costs of most things always heading 'north', it invariably makes it hard for those with young family's to donate very much, to their chosen charity?

We regularly donate a modest amount probably six time per year. Though lately our home address and unlisted 'phone number, have been compromised. Consequently we're being bombarded with requests for donations, from some Charities I've never even heard of? Obviously someone or some group has made a quid or two by selling information? I've been looking into, who it might've been, and have managed to narrow it down to one or two Charities.

Something I never do, is provide a Credit Card when donating, you don't know who works in these charities, and what mischief they can get up to, with one's Card? That aside, I would still like to continue, giving as much as I can, not because I'm a 'goody two shoes'; it's just I feel so damn 'lucky' to have literally 'everything' supplied to me FREE, through the auspices of the Department of Veterans' Affairs (DVA) because of my war service in the mid 1960's. Now it's time for me, to return a bit I reckon!

The best example for NathanJ's very valid argument is tax deductible donations.

Ayn Rand had a lot of negative things to say about Altruism. One of the things about Altruism is it's somewhat arbitrary as to the good due to the zero sum nature of money.