They expect that you are using their service as a way to capture messages that you will want to read or listen too.
What you are describing is a feature for a throw away number full of spam calls where you assume that pages and pages of calls are worthless and should be able to be mass deleted all at once.
If this isn't you, and you DO read or listen to your messages, you can check off each message as you look at them and click archive to make them go away.
For stalkers and other spam, Google Voice has some powerful blocking features. The feature to send missed calls to email instead of your voice inbox is nice. You can even set private greetings for your mom, family or stalkers when they call. Check out all of these features in the settings (gear) on the top right.
If you are still confronted with too many calls to look through after all of that, consider hiring a secretary. 🙂
Why does Google Voice not have a way to bulk delete messages?
