Any modern Apple device, iPhone, iPad, or Mac is basically a brick to thieves while they remain registered to the users Apple ID. They are all protected by Activation Lock.
Putting it in lost mode allows you to leave a message on the screen so if they’re found by an honest person they’ll know how to contact you to return it. Just make sure you never remove it from your Apple ID account and all they’ll be able to do with it is use a few salvageable parts.