It clearly says so in the WhatsApp settings what people can and cannot see. This is the modern day equivalent of cold calling a range of home numbers and see who answers. If you don't want that information to be public, disable it. Simple as that. This functionality is pretty much what made WhatsApp so easily accessible for anyone in the first place.
If you get cold-called, you will catch on that somebody is checking your status (home/not home) or tries to elicit information from you – because you are directly involved. With this API, you'll never notice that somebody tracks you. Most non-tech people will never check the settings tab and even fewer will check the privacy settings. They are not aware they are sharing their info publicly.
>We collect information about your online and status message changes on our Services, such as whether you are online (your “online status”), when you last used our Services (your “last seen status”), and when you last updated your status message.
And
>Your phone number, profile name and photo, online status and status message, last seen status, and receipts may be available to anyone who uses our Services, although you can configure your Services settings to manage certain information available to other users.
"B-but people don't read those!" - well then maybe that's something to worry about instead of complaining about an API which is the nature of the product.