A good many New Testament (NT) scholars have demonstrated the value of reading the NT in light of extra biblical sources -- be those sources literary, epigraphic, numismatic, or archaeological. Hence, the NT scholar finds it necessary to explore the Old Testament Pseudepigrapha, Greek and Latin classics, public inscriptions, images on coins, and the city plans and buildings found within the NT era. All of this leads us to a fuller, and more accurate, understanding of the content of the NT scriptures.
However, where this becomes curious (at least in my own particular area of study) is the way in which the genuine Pauline letters are still, by and large, studied without serious regard given to The Acts of the Apostles or, more especially, the Deutero-Pauline epistles. Why is it, for example, authors like Virgil, Tacitus, and Suetonius are given so much weight in our readings of Paul, while Luke's narrative account of parts of Paul's life is given less weight? Or, to take another example, why is an author like Juvenal considered an useful resource (even though he wrote after Paul did) when the Deutero-Pauline epistles are not (even though they were likely written earlier than much of Juvenal)? Or, to mention an even later work, on what basis can we refer to The Acts of Paul and Thecla while simultaneously ignoring 1 & 2 Timothy?
It seems to me that, given the tensions (and, perhaps, even contradictions) that exist between the genuine letters of Paul and the Deutero-Pauline epistles (especially the later pastorals), it is easier for us to ignore the epistles and find extra-biblical sources that verify what we want to find in Paul. The problem is that the Deutero-Pauline epistles might be closer to Paul than a good many of these other sources.
Perhaps another reason to ignore these epistles is the bulk of material a person would have to address. Academic specialisation leads to narrow foci within scholarship, and it is probably easier to, for example, read Paul in light of Virgil (a relatively unexplored realm, which also makes this more excited work -- and work that is more likely to gain recognition) than it is to read Paul in light of the Deutero-Pauline letters.
Of course, there are scholars who continue to view these Deutero-Pauline epistles as genuine letters of Paul, but, IMO, this is an oversimplification. Rather, what I think we should be asking is 'how was it that these epistles developed out of Pauline communities, and in what ways are they faithful and unfaithful to Paul?'
Consequently, given all the appeals currently being made to extra-biblical sources, I am somewhat baffled that The Acts of the Apostles and, more particularly, the Deutero-Pauline letters are still largely neglected in Pauline scholarship. Indeed, those scholars who engage in 'counter-imperial' readings of Paul (i.e. the scholars I have been reading a lot) should be especially ocncerned with addressing the questions listed above. Rather than brushing aside Acts and the Deutero-Pauline epistles simply because they were not authored by Paul, they need to explore how communities that begin with such a radical founder can devolve into communities that embrace the dominant sensibilities of the empire (if, indeed, the Acts and the Deutero-Pauline epistles do this).