The features aren't random. They're usually related to other features. They might be variations on a feature. For example, what if the user doesn't like the apps fonts and colors? Let's let them customize the look and feel to whatever they want. Or we've made this app that let's you send text messages to people, but what if it needs to be sent to an international number? Suppose this feature is right now unnecessary because the app is just for sending text messages among employees at a company that is situated in Wichita.

These aren't crazy features, but they're unnecessary and may never be necessary. As to "why do their managers and technical leaders allow it," often they are the very people who spearhead it. Or in my case, our team was embedded in a non-software company, and our leaders didn't understand exactly what we did, so they were hands-off.