People sometimes use a more generic CV if they have numerous strings to their bow and want to demonstrate their versatility.

The perceived advantage of this include is that the more skills you demonstrate to the employer the more impressed they will be. However, this isn't always the case, and for the best results you are usually better off specifically targeting your CV for a particular job, or job type. After all, most employers are not looking for people with expertise across lots of different jobs and sectors, in most cases they are just looking for specialists in the job they have on offer. Consequently, in many cases a well-written targeted CV will be more effective than a generic one.