What do you think of people who dont respond to your messages even though they have seen them on Facebook Messenger?

Usually I don't notice they have seen them because I send a message and don't look again. If I notice and it was a question, I give them a couple of days and if they don't answer I think we're done and this person doesn't want to have anything to do with me. If it isn't a question, I just conclude the conversation was finished and they have nothing else to say.