I'd agree in the studio, but don't think I can offer any definitive answer. There are details of course, but also some user preference involved in some cases.
Two very major aspects:
The camera meter cannot meter studio flash. The handheld meter typically can. If using one hot shoe TTL flash, the camera meter can handle it, but which is no help with any manual flash unit.
If we are dealing with ONE flash, we can easily use trial and error to tweak exposure in using the histogram and rear LCD image...
But if we are dealing with multiple flash units, then beyond simple exposure, we also need to set their levels relative to each other, which is lighting ratio... The histogram cannot help with that. It is generally very good to actually meter each light, to actually KNOW what we are doing. The handheld meter is generally NOT optional then.
The camera meter is a reflected meter, which confuses beginners, but for continuous light, we can and do learn how to correct for their idiosyncrasies. The handheld meter is typically an incident meter, generally more absolutely accurate, since it is independent of being affected by the subjects colors. However, the incident meter must meter from the subjects position, not the camera position.
I'm thinking if you plan to take a daylight picture of the scenic pasture field, the handheld meter can do it, and well, but it offers less advantage over the camera meter. Some will think handheld still has advantage, but truly, we can probably manage without it. I have learned how to compensate for a reflected camera meter, so I mostly only use my handheld meter for multiple studio flash, where I consider it mandatory.
