Most of us probably have a number of bikes and use the one that is most appropriate for the circumstances. Why not the same with stoves?
Because this is STW, home of black and white thinking where anything can only be absolutely brilliant or completely rubbish.
JetBoils etc are effectively neat, portable kettles, they’re great for brewing up rapidly and fine for one-pot dehydrated stuff or boil in the bag. They pack down neatly, are reasonably wind resistant – if you want proper performance in wind, take a look at the MSR version, the Wind Burner – and are easy to use.
They’re not great if you want to ‘cook’ properly using more than one pan or a frying pan, although the Primus version comes with screw-in pins to sort of allow you to do this and despite what a few folk have said above, they’re not that stable compared to a remote canister stove.
They’re also not the lightest option by some distance, but it depends on your priorities really. If you want to use a coke can stove with meths, that’s fine, but not as convenient as a PCS.
So it is what it is basically, but you need to understand its limitations and whether they work for your precise needs.