Have stuck with book 1-3 chargen myself. No real thought out reasoning, just they always sufficed for me and my players.
Till MgT, hadn't thought to use anything other than 2D6. For structured systems, the 5 extra values and normal like curve of 3D6 are appealing. Even adapted for a more freeform system, 3D6 elegantly offers a true 50/50 split at 10 (3-10/11-18) and nearly 50% more options for random tables.
For CT style, it would be rare if 2 and 12, at least, weren't fail/succeed, so no magic there. However, natural 2/12 hacks cripple a (detailed) structured system as vastly different DMs become equivalent real quick. Systems like MgT with stat bonuses (esp. with augments), skill level, gear and difficulty DMs - easily saturate 2D6.
Additionally, as I'm using the task system for combat, i.e. with lots of DM potential, I'm loath to put such artifices in.
At the table, I've never had an issue with CT's unstructured system, nor have my players. Give them a target and roll, with DM's rarely figuring in separately and 2D6 being more than adequate. But, applying a structured system universally, including combat, has some appeal I am experimenting with - especially for PbP games.