Some people are cautious, and some like to live dangerously and just don't care to get hacked. If there is no need to expose publicly, why would you take the risk. If you do, you better be 99.99% sure that your setup is secure. Some people are, and a lot think they are.

Clever!

Selfmade nuggets are the best. Because you know what's inside.

There are thousands of reasons.

Spamming dozens of subs is really not a good way to advertise a new product. Good luck.