Not, why should donors give? Instead, why are you raising money?
This is a question about your personal motivations for doing this work.
The least motivating answer: “To build a building (or “start a program,” or “meet the budget,” etc.).
The moderately motivating answer: “To better serve our mission – our students, participants, patients, community, etc..”
The most motivating answer: “To spread more widely the authentic joy that comes when people give generously.”
To do this work well over a long career, to derive deep meaning from this profession, to sustain your enthusiasm even during the difficult and tiring stretches, we are wise to fully and consistently embrace the final answer.
The buildings, the programs, the priorities will change. Even the mission may change.
But the rooted goodness of giving is an unalterable and universal human truth. And, when this notion becomes your primary motivating factor, your impact will become far more consequential than simply raising money.