If the connection dropped while I was away, or my house had an intermittent power cut, that forced the router to re-start (and hence change it’s IP), I would lose all connectivity to the IP camera, and my entire home network as well.
This is because, I wouldn’t know what my home network IP address would be anymore, and hence have no way to contact it.
For instance, the IP address of my website has remained static for the 1.5 years it’s been around.
So the DNS allocation for my website is pretty much stable.
Think of it like the actual phone number of the person.
So if you wanted to contact me with just my name, you’d have to look for something called a ‘phone book’.
In this case, the DNS is the phone book, that translates a name to a number, and the DNS is publicly available. Well, that’s where the allocation from name to IP is dynamically allocated.