A friend of mine was telling about his new Draytek 120 ADSL modem and how reliable it is.
He mentioned that it supports transparent PPPoE & PPPoA bridging.

I didn't get around to asking my friend at the time.
Why is this useful? 

Is it useful in the case where an ISP supplies PPPoA to allow the public IP normally assigned to the router to be directly assigned to a PC running PPPoE? thereby bypassing the need for NAT?

PS: I don't want you to tell me what PPPoE is and what PPPoA is. I know what that is.
Why bridge them?