Some cars use them to "breathe" and some are just posers, but the trend for front or side vents is as big as ever.
The locations ranges quite a bit. Some vehicles have them up front, some on the side and some are in the front or rear.
They are used to help engine bay airflow and permit hot air to exit and keep the cooling system and other components cool, while some air intakes are connected to the engine underneath, creating a ram-air effect. Some even push air into the brakes to keep them cool as well.
There are plenty that are just decorative, and even more available as after-market.