When you say OOB, you mean OODB, right?
Well, here's an example.
It takes me only about half a day to whip up a quick and dirty client for a network protocol, even in a language I barely even know. (I know, because I've done just that about half a year ago, with Ruby.) But, being procedural, the client essentially already has scripted in advance what it's going to do. E.g., I could write it to connect to the server, log in under a specific account, post some messages, then log back out. I could even give the user some degree of interaction through CLI arguments, e.g. let them customize the server, username and password. So far, so good.
The trouble comes when none of that is a given. What if the user only wants to run the client, but not actually connect to anything? What if the user wants to connect, but not log in? What if he wants to log in twenty minutes later? Then things aren't linear any more. And then I'm screwed, because I just can't program this kind of interactivity.
Does that illustrate the issue better?