Unique, timeless, flexible are some of the qualities of a GREAT logo.
Does it work in black & white? Will it work as a tiny icon or on a billboard?
All these factors and more go into Our Process of creating a visual identity / logo / corporate identity [whatever you want to call IT]. Ultimately IT is the face of your brand. IT never stops working and consistency [seeing it the same way over time] gives IT recognition. So consistency in all company collateral aids the audience in this process and ultimately reinforces your brand.
A logo is an essential element to help achieve this; it establishes your brand and adds credibility.