Depends on what you're hoping to get out of the the learning and the conversation. For most people, even being able to carry on a conversation at a dinner party with an expert in the field is sufficient reason to read one of these books.
"Oh your dissertation work is on Ancient Egypt?! That's so fascinating! I read about <pharoah-name> and he's buried at <pyramid-name>. Have you done any field work there?" And so on and so forth. If you can ask relevant questions (which an introductory book will create plenty of in your mind) you'll keep the expert engaged and they'll be gratified that you took a genuine interest in their work.
And if you're conversing with another layperson? "I read the most fascinating thing about mummies the other day! Mummies <say fascinating thing, see if other person is engaged, continue conversation>."
Realistically those are the only outcomes people can expect from reading introductory books. And I'd regard them as being very worthy outcomes.