Why opposite of electrophilic is not Protophilic In organic chemistry , considering definitions of  electrophilic and nucleophilic:

Electrophilic:having an affinity for electrons : being an electron acceptor.
nucleophilic : having an affinity for atomic neuclei (also can we say proton?) : being an electron donor.

So both being opposite to each, why dont we say nucleophilic as protophilic?
Because not all "nucleophilic" agents react equally well with all types of relatively exposed nuclei.  Phosphines are very unwilling to extract a proton but quite nucleophilic if the available electronic vacancy is in carbon or a transition metal.