Some clients put them in different spots. Some lump the inbox as one inbox. Others will split them into groups of people you've DM'd before and a group of new DMs that could be spam since there was no back and forth convo. And some people just don't check them.. Like nostr:npub12hcytyr8fumy3axde8wgeced523gyp6v6zczqktwuqeaztfc2xzsz3rdp4 lol