It might seem intuitive when we say you need to play with your puppy, but believe us when we say a lot of people don't! It's equally important to continue that play from puppyhood into adulthood for your dog. There's a significant misnomer out there that dogs being pack animals need social interaction with other dogs. How often do you hear, "Oh he/she just wants to say hello!" as a strange dog on leash pushes up into your dog's personal space. Or even worse while another dog is off leash charging towards you "Oh he/she is FRIENDLY", more often than not, we see that behaviour with a dog who is approaching with signs of over-stimulation and reactivity including hackles up.
So what does this have to do with play? Everything!!! The point of playing with your puppy is that it helps to solidify a bond between you and your dog. It provides neurostimulation and helps relieve boredom. By solidifying that rapport you have with your dog, you are well on your way to reinforcing YOU as their point of interest. Why does that matter? Well it means you'll have a happy, well rounded animal you can exercise and take many places if your dog is always attuned to you.
What do you mean by play? Games like tug of war, fetch, hide and go seek, but the possibilities are limitless. Play can also occur in the form of relationships between dogs in the same household or between known canine friends, but this should never replace the role of YOU playing with your dog.