Can you explain why that’s necessary on a visual approach in vmc by day?
No I cannot. I only did 2 years on the A320 - but that was my general 'experience' of the operation overall.
I will give you one example that may illustrate the dilemma in a British airline:
A Captain I know failed his command check on B737 because he had a late visual swap to a parallel runway in VMC and insisted it was changed in the FMC.
In the same issue in an A320/etc it seems it is imperative that a pilot provides inputs to the FMGC.
Personally I believe that the visual swap to the parallel runway without reference to FMC or FMGC is the better option - always assuming of course that you have thoroughly briefed for all the go-around eventualities - or if you haven't get on to ATC fairly quickly.
Regards
Exeng