In addition to what has been said, I believe what makes things more difficult is that a number of those signing up don't read the information that is provided, beyond the headline at least, which is why an always on goodybag is often refereed to as 'all you can eat'.@harrrrrry
makes some very good points in the mail above, but the idea of 'bundles' and credit, is not unique to giffgaff it is common to all PAYG offerings, the implementation varies from company to company, and in my view giffgaff is clearer than many.
Where the problem in my view starts however is with the retail packaging, that all that is necessary is to 'top up' £10 to receive the bundle described.
Recently the packaging convinced Argos the SIMs were preloaded with a goodybag and hence they included this in their description and charged £10.
The trouble then is if someone has bought a SIM believing that topping up £10 will give them a bundle , what they are then confronted with does become confusing, and some merely top up.
I know that giffgaff present the SIMs the way they do for marketing reasons, but it can cause confusion during activation.