Your survey is inactive for the following reasons:
Quality Control
The survey cannot be taken by recipients and allows you to review it before it can be taken.
Ease of Building
In "Edit Survey" you have access to quick and simple build modes that are not available with active surveys.
Data Integrity
Since no one can take an inactive survey you don't need to worry about invalidating your data. Once data has been collected you must be careful not to invalidate results when modifying the survey.
A survey should not be activated until you are ready to collect responses from recipients.