p: messages (PrimeFaces) funciona mas h:messages não | Java e JSF I: Sua aplicação web com JSF2

Olá, notei que que o h:message ( http://java.sun.com/jsf/html) não funciona no Codigo abaixo, mas o p:message do Prime faces sim. Podem me explicar o porque?

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
    xmlns:ui="http://java.sun.com/jsf/facelets"
    xmlns:f="http://java.sun.com/jsf/core"
    xmlns:h="http://java.sun.com/jsf/html"
    xmlns:c="http://java.sun.com/jsp/jstl/core"
    xmlns:p="http://primefaces.org/ui">
<h:head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
    <title>Agenda Java - Login</title>
</h:head>
<h:body>
    <h:form>
        <p:messages id="messages" showDetail="true" autoUpdate="true"
            closable="true" />
        <p:fieldset legend="Login" style="margin-bottom:20px">
            <h:panelGrid columns="2" cellpadding="5">
                <p:outputLabel for="login" value="Usuário" />
                <p:inputText id="login" value="#{loginBean.usuario.email}"
                    validator="#{loginBean.validaemail}" required="true" >

                </p:inputText>
                <p:outputLabel for="senha" value="Senha" />
                <p:password id="senha" feedback="true" inline="false"
                    value="#{loginBean.usuario.senha}" required="True"
                    requiredMessage="Insira a senha!" />
                <p:commandButton id="submit" value="submit" type="submit"
                    action="#{loginBean.login}" />
            </h:panelGrid>
            <h:messages />
        </p:fieldset>
    </h:form>

</h:body>
</html>

package com.agendajava.bean;

import javax.faces.application.FacesMessage;
import javax.faces.bean.ManagedBean;
import javax.faces.component.UIComponent;
import javax.faces.context.FacesContext;
import javax.faces.validator.ValidatorException;
import javax.xml.bind.ValidationException;

import com.agendajava.Dao.LoginDao;
import com.agendajava.model.Usuario;

//@WebServlet(urlPatterns = "/login")
@ManagedBean(name = "loginBean")
public class LoginBean {

    Usuario usuario = new Usuario();

    public Usuario getUsuario() {
        return usuario;
    }

    public void setUsuario(Usuario usuario) {
        this.usuario = usuario;
    }

    public String login() {

        if (new LoginDao().login(usuario)) { 
            return "contatos?faces-redirect=true";
        } else {
            FacesContext.getCurrentInstance().addMessage("submit", new FacesMessage("Login ou Senha Incorretos!"));
        }

        return "Falha na Autenticação";
    }

    public void validaemail(FacesContext fc, UIComponent component,Object value) throws ValidatorException{

        String valor = value.toString();

        if(valor.contentEquals("alexandre")){
            throw new ValidatorException(new FacesMessage("Você é o Alexandre você não pode Entrar"));
        }



    }


}