what are the benefits of using service pages in asp.net projects

using System;
using System.Collections;
using System.Linq;
using System.Web;
using System.Web.Services;
using System.Web.Services.Protocols;
using System.Xml.Linq;
using BusinessLogic.BLL;
using System.Text.RegularExpressions;
using DataAccess.DL;
using System.Collections.Generic;
using System.Web.Script.Services;
using System.Data;

namespace TravelAgency.Services
{
    /// <summary>
    /// Summary description for User
    /// </summary>
    [WebService(Namespace = "http://tempuri.org/")]
    [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
    [System.ComponentModel.ToolboxItem(false)]
    // To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line. 
    [System.Web.Script.Services.ScriptService]
    public class User : System.Web.Services.WebService
    {

        [WebMethod]
        public string HelloWorld()
        {
            return "Hello World";
        }

        [WebMethod(EnableSession = true)]
        public string RegisterUser(string Title, string First_Name, string Last_Name, string Email, string Ref_No, DateTime ADate, string ATime, DateTime DDate, string DTime, int N_F_Nights, string Room_Type, int N_F_Rooms, int N_F_Adults, int N_F_Child, string Booking_Terms, float Amount)
        {
            BLLRegister objBLL = new BLLRegister();
            DLRegister objDL = new DLRegister();

            string res = "";

            objDL.TA_Title = Title.ToString().Trim();
            objDL.TA_Fname = First_Name.ToString().Trim();
            objDL.TA_Lname = Last_Name.ToString().Trim();
            objDL.TA_Email = Email.Trim();
            objDL.TA_BookingRefNo = Ref_No.ToString().Trim();
            objDL.TA_ArrivalDate = Convert.ToDateTime(ADate);
            objDL.TA_DepDate = Convert.ToDateTime(DDate);
            objDL.TA_Nights = Convert.ToInt32(N_F_Nights);
            objDL.TA_RoomType = Room_Type.ToString().Trim();
            objDL.TA_Rooms = Convert.ToInt32(N_F_Rooms);
            objDL.TA_Adults = Convert.ToInt32(N_F_Adults);
            objDL.TA_Child = Convert.ToInt32(N_F_Child);
            objDL.TA_BookingTerms = Booking_Terms.ToString().Trim();
            objDL.TA_AmountDue = Convert.ToInt32(Amount);



            if (objBLL.RegisterUser(objDL))
            {



              


                res = "Success";


            }
            else
            {
                res = "Failed";
            }
            return res;
        }

    }
}