Is this normal?

AB

My LO is almost 7 month old but he doesn’t really talk back whenever we talk to him. He used to talk a lot to himself when he wakes up from his nap or in the middle of the night. Now he still does a little here and there but hardly talks back to us when we talk to him. He’ll just smile mostly. Is this normal? I thought that by now most babies talk back when you talk to them?