Why do SparkFun make breakouts for circuit multiplexers?
Because sometimes you want to prototype with the newest or devices with more features. Hobbyists often do not have access to in house fabs just for initial prototyping, while they will eventually get full pcbs made. And because some are more follow the Ikea instructions type of people instead of looking to replace similar but not exactly the same parts in someone else's project they are copying.

And obviously, they make them because there is a market for them. Economic tautology.