It's up to the developer to make user friendly products (just like software [annoyances], bad practices, etc.).. If the captcha is done correctly, then it shouldn't be too much of a problem to pass.. Then again, they (some developers) try not to make it too easy, for obvious reasons.
Unfortunately you're wrong there. (I posted about it here
The ability of machines (software) to solve CAPTCHAS is so good, that you can no longer create a CAPTCHA that is reliably easy for a human, but difficult for a machine. The same goes for audio versions.
The RECAPTCHA project poses a solution to this problem, however, if you look at it closely, they're processing a LOT of text automatically, then choosing the ones that are specifically difficult for machines. However, this is not currently an apriori type of thing that you can do. It relies upon experience in seeing that a machined failed for a specific word.
The downshot is that no matter what you do from a development stand point, you will fail. The moment you make a CAPTCHA that is reasonable for a human, a machine can solve it easier.
It's really a catch-22.
For more information, search for stuff like "cracking captchas" or "captcha ocr" etc. You'll see that there's a wealth of information on how to do it.