The power of the New Birth

In line with my post yesterday ( What do you do with I John?), I thought I would post a few more thoughts on the new birth. Scripture is quite clear that when someone becomes a Christian, they become a new person (go ahead and compile your own list here, I'm sure you can...). But, what we forget is what happens to the old man/person (inclusive language really fails here!)—Romans 6 is clear about it:
οἵτινες ἀπεθάνομεν τῇ ἁμαρτίᾳ, πῶς ἔτι ζήσομεν ἐν αὐτῇ; ἢ ἀγνοεῖτε ὅτι, ὅσοι ἐβαπτίσθημεν εἰς Χριστὸν Ἰησοῦν, εἰς τὸν θάνατον αὐτοῦ ἐβαπτίσθημεν; συνετάφημεν οὖν αὐτῷ διὰ τοῦ βαπτίσματος εἰς τὸν θάνατον... (Romans 6:2b-4a)
“How can we who died to sin still live in it? Or do you not know that as many as were baptized into Christ Jesus were baptized into his death? Therefore we have been buried with him through baptism into death” (NET Bible)

So why does our theology not allow for this? Is it because we don't see it? Maybe the reason we don't see it is because it isn't taught? What do you think?