The reason why you are packing is generally because you want to bring your precious belongings to your new home so you can continue to use them. So, the very first reason why you need appropriate packing materials is to be able to transport your things successfully without damaging any of them. For one, you need sturdy boxes. Otherwise, the boxes wouldn't be able to hold the heavy items inside it. It could get torn as you or the movers lift them. If are carrying fragile items, they would surely get broken.
Even if you have sturdy boxes, you also need to provide cushion for delicate items. The aim is for each piece inside the box not to shift and not to bump each other. In fact, the rule of thumb is for you not to be able to make out the shape of the item. Even if the objects shift while in transit, they would not easily get broken. That is why you should buy bubble wrap, peanuts and packing papers.
Of course, it's quite self explanatory why you need tapes. You need to seal the boxes on top and at the bottom so your things will not fall off. You also provide more support for the weight when you tape the boxes crosswise across the middle. To effectively do so though, make sure you choose good adhesive and sturdy packing tapes as well.