And there's a MacMillan cancer support advert on my page already (not that I have anything against them).
Even with charities mainly staffed by volunteers there are generally some wages and overheads to pay. Paying for websites, advertising, leaflets etc etc etc.
One way to maximise a particular person receiving money e.g. something like giving a cancer patient £50 to help pay expenses for travel to hospital, food etc would be to volunteer yourself, get to know people with the illness and put money in an envelope with their name on it and send it to them.
If you want money to go into research that is a very expensive and time consuming thing to do. Often the research staff have to work in the field as donating one day out of a life of doing another job every so often gives no consistency in research. How can you grow something in the lab and not come back to it until your next day in next month, it needs looking at and acting on sooner. You can't rely on everyone else to look at your research, they'd have to know what you were doing when and take time out of their one or two days a month volunteering to check your stuff.
So they need staff and money to pay wages, so they need staff to raise money. So they need to pay those fundraisers, so they need to pay people to fund fundraisers, so ultimately they need to pay CEOs to organise those staff and to be the face of these charities. The CEOs etc can and do bring in big money as well, they know the people with big money.
I, as a volunteer, don't necessarily know the owners of multi-million pound corporations, but the people who run big charities and businesses are more likely to know millionaires. A lot of the people at the top of these charities can be big fundraisers, so don't be too quick to not be willing to help fund their wages, they are needed too.
(And no, I am a sahm not a CEO of a charity, so I am not asking you to pay my wage.)