system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do spam ads bother allowing you to close them?

No matter how annoying, they always have an "X" to allow you to close them.

Since they are spamming anyway, why not go all the way and not allow you to close them at all?

Is there some kind of law they are following?
gpt
By giving you an X to find they ensure that you engage with them on some level, hopefully ramming some aspect of their content into your consciousness. 

Another issue is that by giving you a method of avoiding them they hopefully keep you from searching out a way to get rid of them entirely such as ad blocking software.