TLDR Answer: Because your logo will have to show up in more than one spot and you want it to look good every time.
Ok, let’s break that quick answer down a bit.
What does it mean to have more than one version of your logo?
At its simplest form, it means having various lockups of your logo, or layouts. For example, you will have a primary logo that may include a brand mark (icon) and wordmark (text of your business name) that is stacked with one on top of the other.
But what happens when there is not a lot of vertical real estate for your logo? Well if you don’t have an alternative layout it could mean a really small, hard-to-read logo as you try to make it fit.
Instead of letting your logo be super tiny, it’s best in this case, you could use an alternative that moves the icon to the side of the wordmark creating a more horizontal layout that fits in the space without a lot of vertical real estate.
Another commonplace to consider an alternative logo for is the small circle boundaries of a social media profile picture.
What variations do you need?
Logo variations don’t need to stop at the layout for size.
Consider use cases.
Is there a need for you to have variations to signify internal vs external brand, or a more formal identity mark signifying something as official from your brand? This could look like a badge variation of your logo.
You might need a sub mark or watermark to place over your copyrighted pieces that isn’t obtrusive but still identifying to your brand. Perhaps this is initials or more formally a monogram.
Do you need a version with a tagline or established dates? These are also variations by use case.
How about color variations?
This may seem obvious, but your full-color version of your logo won’t always be possible to use. It may clash with a background color or not be visible because of a similar color used in both the logo and background. OR printing it for a sign, promo product or decal may require a single-color option.
Ideally, you want full-color, black, white, and single-color versions of your logo.
The single-color version will often be your primary brand color, but if you have multiple primary colors or if you see a need for a second single color’s use, you can also define a second single-color version of your logo.
Curious about why a black, white and single-color version is so important? I answer why I start with B&W in logo design on Instagram.
Lastly, print vs web
The last variations to consider are a print version and a web version of each layout, alternative, and color.
Why? Because they are different.
Print requires a higher quality image (300dpi) to print clearly and prints with CMYK (cyan, magenta, yellow, black) colors.
Web requires a smaller file size (72dpi) to be viewed clearly AND for optimizing load speeds and is viewed in RGB (red, green, blue) colors.
When I work with a client, I make sure all of these variations are covered.