Its absolutely a best practice! you don’t want to mix all those utility functions with the rest of your application business logic. However, as your utils files and/or classes grow it is recommended to group them according to the function they provide.
For example, in a web application you could end up with a package structure like this.
org.sample.web.model
org.sample.web.utils
org.sample.web.validators
org.sample.web.validators.utils