I've said recently that we tend to overlook affordances (see here for some more examples and elaboration of this notion) when we evaluate software, because we tend to look at software in exlucively functional terms.
Here's another reason we do that. First, remember that motiviation has a big impact on the things we do:
What acts on your motivation to do things? There’s always costs and benefits associated with doing anything. There’s always multiple things you could be doing. If you do this thing, you’ll miss other things. It always takes some physical/mental energy to do things. You’ve got limited time. You’ve usually got a number of things you need to keep track of at any time (even if you don’t need to put much conscious effort into them). And even a simple task, can distract you from that.That last point applies especially to using software. Each click, each function you perform -- often the amount of benefit associated with it is quite small. So the cost has to be tiny. And that cost can be where two different bits of software that allow you to ultimately do the same things can differ. If the cost is too high and performing that function isn't absolutely necessary, then are you going to bother doing it? Different costs mean different affordances.
Something less obvious is that the ‘benefit’ of doing tasks is often very small. Probably the majority of things we do are like this. And that means that the ‘cost’ of doing it has to be tiny, if we’re to feel motivated to actually do it.
But more than this, we tend to underestimate the force of emotional factors such as motivation. So it's very easy to look at two bits of software with compariable functional capabilities, and -- overlooking the force of motivation -- think that performing the functions in them is simply a matter of wanting to do them.
Which sounds like a weird thing to say: of course performing a few mouse clicks is just a matter of wanting to do it. You just need the connection between that desire and the movements of your hand, right? But when you're actually in the situation, and the possibility of performing the action comes up, you'll be actually experiencing the positive or negative force of motivation that can make it far from a no-brainer.