You make an excellent point. Giraffes also have the same type of selection pressures. People assumed that giraffes had long necks because it allows them to reach higher leaves. There's some truth to that but it's also true that male giraffes compete by pushing each other with their necks.
Anyone seeing a giraffe eat would make the first assumption, only someone seeing male giraffes during rut would notice the second.
Unlike the peacock, the long or thick neck may not hamper a male giraffe's viability