Assuming you have a good solution at a fair price, sales presentations and proposals fail for two reasons:
1. Poor sales activity.
2. Poor communication of the solution.
During sales (also called "capture" for some) you need to understand your future client's real needs. You need to establish rapport, if possible. Your future client is risk adverse. They buy what they trust. They trust what they know, what they are familiar with. You need to speak their language. (What do they call their current solution? What acronyms do they use? What are their goals? What is their mission?) Sales activity needs to uncover this information and help establish rapport. If it is impossible to establish rapport with your future client, create mind share. Own a space in their mind. (Think marketing and repetition.) When your future client thinks of X (whatever is linked to your solution) make sure you or your company pops into their mind.
You have very little time to communicate why your future client should care. Quickly give them an overview of your solution and show them how they will benefit. Most sales presentations and proposals bury the solution in wordy descriptions and mountains of text. EVERY decision maker and evaluator I have interviewed says the same thing, "Make it easy for me to understand your solution and I will probably choose you." That is why visual communication plays a major role. (Graphics communicate solutions up to 60,000 times faster than text, go right to long term memory, quickly affect people emotionally, and are proven to increase success rates.)
It is a misconception that all graphic designers are good visual communicators. Many are good renderers (they can use the tools available to make attractive graphics) and some are good conceptualizers. What I mean is that many designers are good artists and some are good at turning text, ideas, and solutions into clear, compelling visuals. (My fellow designers know where their strengths are.) The same is true for writers, engineers, accountants, lawyers, scientists, business professionals of all types. We have our specialties. We have our strengths and weaknesses. Designers are the same.
In the end, most sales presentations and proposals ignore visual communication all together or ask a talented graphic designer who specializes in rendering to do conceptualization. That's like asking a plastic surgeon to do brain surgery. After 20 years, it kills me to see beautiful graphics that communicate very little if anything at all.
Assuming you have a good solution at a fair price, if you put forth the right sales effort and communicate your solution quickly and clearly (giving your future client a reason to care) you will succeed. Don't believe me? Try it for yourself or email me: email@example.com. I'll share countless true stories of success and failure from big and small companies alike. Now go help others, spread the word that your solution is the best, and be successful!