Why does the apple sauce container have ridges and grooves? Could you not use a smooth container?

Why does the apple sauce container have ridges and grooves? Could you not use a smooth container?

Our apple sauce container was designed to withstand the effects of a "hot-fill" process. The indentations help maintain the container structure during this process.  The smooth walled plastic packages you may be familiar with (such as peanut butter) are “cold-filled” and don’t experience the same temperature fluctuations.