Let me start off by saying that this is a loaded question!
There will be some that say artistry is in the eye and so they like to eyeball their shot. Others may argue that photography and lighting specifically is about precision, and that a light meter will help you with precise ratios. I'm simply going to tell you why I like to use a light meter and how it helps me in my photography.
First my opinion…
I honestly feel like those who believe they don't need a light meter are most times just starting out. Often times it's the same argument as being a natural light photographer, they're just a bit intimidated by using strobes. This doesn't include those who have been doing photography for many years and already know what their lights will be set to ergo not needing a light meter.
But, I'm here to tell you that there's nothing to be afraid of in that light meters only assist in measuring light more quickly.
Take this shot taken for a client as an example:
This could've taken quite a while and quite a few shots to figure out the perfect exposure. However, metering for the background and then metering my subject allowed me to get the complexity of the shot much quicker. I use the Sekonic LITEMASTER PRO L-478D.
My client for this shot wanted something moody for this set. As you can see there's all a lot of contrast in this shot. A lot more darks then there are lights. In this case, since my light meter is able to tell me the dynamic range of my camera, I was still able to bring out detail in darker areas such as her hair.
One of the more important uses of a light meter is the quickness in which you set up shots as I mentioned above. When you're with a client, you don't want to keep on waiting by guessing your light. Simply being able to do it quickly just shows another level of professionalism.
So, can you do photography without a light meter? OF COURSE!
The purpose of a light meter is to help and aid in getting proper exposures and desired light ratios quicker then you would test shooting. Remember, it's only a tool!
Let me know what you think about light meters. Do you use one? Do you think they're necessary? Comment below!
Checkout Adorama for their light meters