The built-in tuner of my Icom IC-7300 can only tune up to an SWR of 3:1 without enabling the emergency mode, this emergency mode will limit the power to 50W average power. As I want to have the possibility to use more power if I need to, an external tuner is the only way to go.
I have bought a Daiwa CNA-1001 and use it to tune my 10/20/40m End-Fed for other bands, e.g. 17 and 80 meter.
Of course I know it's better to have a suitable antenna for those other bands, but now I can work on other bands than what my End-Fed is designed for, at least until I have the right antennas for that.
The manual states that the tuner can't handle an SWR higher than 5:1, my experience is that my tuner can tune an SWR of over 10:1 to below 1.5:1 as indicated by the built-in SWR meter.