If I can write awesome code, why should I care about having visibility? The work I am doing rocks, then why should I think about standing on the roof top and telling about it.
The important thing to realize is - no one cares about what you do at work. No one cares how great your code is. How awesome your widgets are.
What matters is how people perceive your work. How good do they think your work is?
Is this unfair? Do you think "my work should speak for itself?"
This is simply not how it works. If you do quality work and are hated because you are antisocial and arrogant and rude, people will think lower of your work. If you do quality work but no one knows, people will not think highly of your work.
PIE - Performance, Image, and Exposure
There is an idea called PIE for factors affecting career success. Most agree they are important, but don't think in these proportions.
This article contains the following graphic as well as considerable more detail on this idea.
Maybe these percentages are off slightly. But unless you are a complete screw-up your actual day-to-day performance is a much much much smaller piece of the impression people have of how well you do your job than you want to think.
What if you still don't care?
Maybe you still don't care. But if you are hoping to have a successful career (whether promotions, high salary, freedom to easily change jobs, not being first in line to be laid off, etc) these things are important.
If you don't mind if people who are "worse" at their jobs get higher salaries, better promotions, and seem to have more options, then you don't have to care.
Interestingly, this question is in the "hot questions" list. The visibility provided to The Workplace through this is beneficial for the overall health of the site (unless people post low quality questions/answers) in a manner similar to exposure in your career.