I am forever being asked if I am a bot, simply because I am so active, especially with the edit button. Can someone write a program that I can click on and it will do it for me?
We need Captchas to prevent bad behavior. Someone could easily write a program that would create lots of bad edits or ask lots of bad questions. Stack Overflow could be overrun with spam.
Even though you have some rep, having Captchas in place minimises the amount of damage you can do with your account and also minimises the amount of damage others can do with your account. It's a safety net.
Also, the whole point of a Captcha is that humans are able to solve them and programs can not. If someone could write a program to accomplish this, the Captcha would be outdated and a new one would have to be implemented.