External USB FLASH drive for /overlay vs internal?

I see many people using an external USB FLASH drive to store the /overlay files, mostly because it can provide more space than what is supported by the internal FLASH.

I have a Netgear R7800 which provides plenty of space in /overlay with the internal FLASH.

Is there a compelling reason to use an external FLASH drive for /overlay?
I presume it would "save" on the "wear and tear" of the internal NAND FLASH of the device.

Thanks for any advice.

-- Steven

IMHO low flash space is the only reason why one would need extroot.

+1 to @tmomas .

But, there is also one more 'fun' extroot factor that can be useful in some circumstances...
When you pivot to extroot, you basically copy your 'current' configuration from the internal flash onto the extroot drive. Once you're running the extroot setup, any changes you make are applied to the extroot environment. As a result, you can simply unplug your extroot drive and you'll be back to your pre-extroot configuration instantly. This can be really useful if you're experimenting and especially if you might break things. Beyond that, you can insert that drive into a normal computer and copy files or edit them directly on your computer.