The DP has a multi-pair cable entering it and individual pairs exiting it which lead off to the various premises.
The fibre manifold has a fibre feed entering it and individual fibres exiting it which lead off to the various premises.
Suppose it was physically possible to accommodate both metallic and fibre connections within a dual-purpose DP, what would happen when a standard metallic pathway service develops a fault which requires a technician to access that (hypothetical) dual-purpose DP? If it is just a PSTN (metallic pair, telephony trained) technician, blundering-
Barry or nervous-
Nora, should s/he be allowed to access a device containing fibre junctions? Or will he have to defer the fault fixing to a multi-skilled technician, a super-
Black Sheep?
Now consider what the fitting of that (hypothetical) dual-purpose DP would entail. All existing services via the old metallic DP will suffer a service interruption whilst it is disconnected and the new device is fitted. Would you be happy with that state of affairs if you were served by that DP and had no interest in fibre feeds, etc?