If done tastefully, you can promote your products or services on your voicemail greeting without sounding pushy. In fact, it’s a great way to keep customers up-to-date on company events, sales, and other news. Be sure to keep it short and have fun with it.
Context does matter here. If the caller would reasonably expect you to answer the phone (such as if they were calling a store or other place of business), an apology for not being able to get to the phone makes the most sense.

The bottom line is that a business’s situation is likely to change often and rapidly, each of which need a unique and applicable voicemail greeting to cover the circumstances and timeline. For example, callers shouldn’t reach a business-as-usual voicemail, and therefore expect a return call within the business day, if the subject they’re calling is out on vacation for two weeks. Such a lack of communication is a recipe to lose that caller’s trust and tarnish the brand’s reputation.
If a call happens outside normal business hours, you can create a specific auto-attendant that’ll handle those calls with an alternative greeting message and menu options. An auto-attendant is an excellent option for businesses with regular working hours, but you might need a more robust solution if you plan to offer 24-hour service.