Far from not knowing what you're doing with GUI partition programs you can see the partitions laid out in front of you, when you shrink them you drag them to make them smaller, etc. At all times you can see what's going on in a way that's understandable by most people.
Now with fdisk its a rather cryptic and very simple interface, the average user would have no idea what it means or how to use it. Even though with *fdisk you can go into a lot more detail and have a lot more finer control over what you're doing.
Anyway the real problem with *fdisk is that it cannot preserve data when resizing partitions.
Many a time one may let down by a distro and forced into the terminal mode. Expert in using Diskdrake, diskdruid and qtparted can't go very far as these programs need GUI to run.
You would do any partitioning from a LiveCD anyway, so it doesn't matter if you break your distro. Any computer which doesn't/can't have X windows on it is only going to be usable by people skilled in the Linux shells anyway so they'll be able to use *fdisk.