You still own the BF4 music, why not just put it back in?

I would think EA/Dice would love each of their titles have own "sound identity", therefore a reason why they don't do it often.

I do agree, BF4 OST is great, but lets see what they will come up with for BF6 release OST.

completly unrelated but does bf6 just not work on intel arc aseries cards?

There are known issues with arc cards 

Its what Amp said, its a new game so they'll give it its own identity. Maybe if they reintroduce some battlefield 4 maps they will come with their original soundtrack