Proposal writing is very complicated. If you're writing a proposal to publish a book, that's very different than writing a proposal for a grant. This is a niche market in which writers with very specialized skills know the standards and requirements for replying to RFQ's (request for quotes) or RFP (request for proposals.) When I worked for Texas Instruments, we had a staff of 45 people to process our proposals for government contracts, which tells you how complicated the process was.
Proposals are sales pitches, just in a more complicated manner than what an individual sales person would do. The folks who consistently are successful with their proposals know their audience and what they're looking for. That's why there are so many books for writers about how to submit a query letter or book proposal. It's a formula, but it's unique to every publisher.
Grant-writing is another level of proposal writing that is even more complex. Most foundations have a detailed process, often the application is submitted online. Because foundations have been hit hard by the recession, the odds are even higher against getting accepted. Apply for a grant is not a process that you undertake casually without a lot of thought and preparation.