"Cracking" in this sense is brute forcing. SHA1 is fast, and people use bad passwords. The combination means that you can run through lots and lots of bad passwords very quickly. I checked my linked in password I have stored in 1password, and it is 20+ chars with special characters and numbers. That won't be "cracked" in any meaningful sense, so I don't even worry about it.

You are correct that there's currently no way to go from a hash to a value that hashes to it in SHA1 (AFAIK, IANYNSA [I am not your NSA]).