It's not so much whether you have extra curricular on your CV or not but rather the skills which you would've developed from being actively involved in those extra curricular things such as leadership, teamwork, time management, delegation, planning, interpersonal skills, etc... all of which are genuinely of importance in the real world. The other side of this is you will also be placed in situations which require you to make (potentially difficult) decisions and past performance can be an indicator of how you'd respond if facing a similar situation at work.
These are things which you don't get by reading books. After all, academics are one thing, but if you're fresh out of high school, how much relevant-to-the-job knowledge do you think you have?
It's all taught on the job so if you're trying to stand out from the crowd, get involved and hopefully you will learn something.
Back to your extra curricular topic though, there is of course the substitution for say, work experience. Both of these avenues give you opportunities to develop new skills, as well as give you responsibility.
ps. This also applies to grad jobs, but at that level, you'd be expected to have significantly more experience or skills.