Because you can't spot the cookies, and even if you could, you couldn't re-use them.
An actual HTTP request looks something like this, and the whole thing is encrypted:
GET /wiki/Main_Page HTTP/1.1
User-Agent: Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/31.0.1650.57 Safari/537.36 OPR/18.0.1284.49
Accept-Encoding: gzip, deflate
Cookie: centralnotice_bucket=0-4.2; uls-previous-languages=%5B%22en%22%5D
Note that the cookie is mixed in with a whole bunch of other stuff. You can't grab an encrypted cookie because you can't find it (it's surrounded by stuff that varies from browser to browser and even request to request). Even if you could find it, SSL includes measures to prevent an attacker from re-sending a request (a replay attack), and it includes a message authentication code (MAC) to prevent an attacker from slicing up a request and only using part of it.
Further, SSL uses a different encryption key for each connection. Even if you could grab the encrypted cookies and bypass the MAC, you'd find they were encrypted with the wrong key for you to use them.