Generally, some people in the non-profits are "multipliers", while others are merely "additive". If you are a smart and educated person, you probably don't want the "additive" role, e.g. one of dozen people who pour the soup at the soup kitchen. Just send some money instead and let someone else do the job; they will do it almost equally well.
But you might be very useful in the "multiplier" role: someone who solves the logistic of soup cooking and distribution, or who speaks with the media, etc. You would be a great multiplier if that role happens to be your profession, but even generally smart people (e.g. someone smart enough to recognize problems and ask online for solutions) could be a big improvement over someone stupid in an important role.
If you want anything done, in any branch of relief work, you will forget the word 'stupid' and be offended on others' behalf if it is used in your presence. It doesn't even take altruism.
As to multiplier/additive equilibrium, yes, causes need multipliers. What I disagree with is that causes will always benefit, linearly or otherwise, from hiring additives.
You start donating money. There appear hired people. The 'free' people gradually leave. You hire more to replace them. Other kitchens, which might not have lawyers in their staff, decide your kitchen can't play nice. You lose their cooperation.
Result: your own utility goes up, the kitchen's goes down.
1. The ordinary hour.
When I read about the lawyer working at the soup kitchen instead of spending another hour at his paying job, I keep thinking, 'how cute these choices are. There are so many lawyers already, and so many kitchens, the guy can hardly say he's on the front-line... he found a way to occupy an evening, less depressing than watching the news.' (If anybody can just pay others to fill in, why doesn't the kitchen already hire help? If it did, surely the lawyer would one day donate money. Charities don't work like clocks, the need for extra funds would arise eventually.)
If the lawyer doesn't come at all, and other people don't come, the kitchen won't work. Even if a handful keeps coming, they won't hold out for long. I have seen it happen. High turnover rates are ok if new volunteers keep stumbling in, but when you come out in full force of five or three, you get this feeling. Like you're the Last Fools on Mars.
And then you all quit.
And then you don't start again. And then you never learn the effect of not contributing anything, and will be discouraged from donating to any cause, because this will be your new default setting. So even if the lawyer allocates one evening for manual labour, he already benefits the cause by being there, which is more than just his personal warm fuzzies.
2. That one hour which you really shouldn't have missed.
Sometimes, asking people to donate money is difficult because you would lose too much by being seen as for-profit, and asking people to donate time is difficult because you have to be absolutely sure they will follow orders. And then the lawyer who comes out of his own volition is worth very much.
Our NGO's hazy mission was protection of wild nature. One of traditional ways to do it is by focussing on specific species, or groups of species. Operation 'Snowdrop' is an umbrella covering prohibition of trade in endangered plants; it starts around late January and closes around late June, but it peaks around February 14 and March 8, the black days of mass destruction.
Now, the problem with people buying endangered plants can be attacked from different angles.
One is educating them. Writing to militsia (police) was the most targeted correspondence, but the most it did was make them wary and derisive (unless they suddenly needed to show activity to their superiors.) We contacted schools, but children usually don't buy flowers; and it always took so much time. Mass-media occasionally took up interest, but for real coverage they wanted Action. Since this provided us with the largest audience, we tried our best to provide it.
We invited them to the train station, where the plants arrived in bulk (mostly snowdrops and cyclamens from the Crimea and crocuses from the Carpathians). There we enlisted police's help and confiscated the flowers, counted them, wrote protocols which would hopefully end up in court and directed the flowers to hospitals. A reporter and a law-enforcer would typically go there with one of us, to witness the distribution. Once, a man demanded before the cameras than we destroy them, so that he would know we didn't cheat him out of profit. The police supported him. That was a devastating hit. We would be reminded of that event for years to come. Explaining that this wasn't what we had planned, or that the flowers were already cut and dead, or that this was one party out of likely ten from that train alone fell on deaf ears - people saw us trampling 10 thousand snowdrops into pulp; we were guilty.
...maybe it is possible to raise funds for this kind of work, but we never figured out how. Office supplies we already had, through association with another NGO. 'For insurance'? (There was that time when it was the cops who trespassed upon a population of Pulsatilla nigricans we monitored.) But men and women, thinking on their feet, not quitting after the first large loss, we never had enough. Now imagine that the lawyer's interested in wild nature protection. What would he rationally do?
(What tags should I use?)