you could say historical reasons, in that dynamic libraries are generated using relocatable position independent code (-pic), which incurs some performance penalty vs code where the linker fills in all the relocations. my guess is thats somewhere around 10%? historical in the sense that that used to be enough to matter? idk that it still is

personally I think leaving the binding of libraries to runtime opens up alot of room for problems, and maybe the savings of having a single copy of a library loaded into memory vs N specialized copies isn't important anymore either.