Why does the default gateway route entry disappear after restarting the network service in RHEL?

Issue

• After a network service restart or a server reboot, the default gateway entry disappears from the IP routing table:

[root@test sysconfig]# netstat -nr
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
192.168.1.10    0.0.0.0         255.255.255.0   U         0 0          0 eth0
169.254.0.0     0.0.0.0         255.255.0.0     U         0 0          0 eth0
0.0.0.0         192.168.1.1     0.0.0.0         UG        0 0          0 eth0
[root@test sysconfig]#
[root@test sysconfig]# service network restart
Shutting down interface eth0:                              [  OK  ]
Shutting down loopback interface:                          [  OK  ]
Bringing up loopback interface:                            [  OK  ]
Bringing up interface eth0:                                [  OK  ]
[root@test sysconfig]# netstat -nr
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
192.168.1.10    0.0.0.0         255.255.255.0   U         0 0          0 eth0
169.254.0.0     0.0.0.0         255.255.0.0     U         0 0          0 eth0
[root@test sysconfig]#

• The interface has a static IP with the parameter GATEWAY in /etc/sysconfig/networking-scripts/ifcfg-eth0
• Why is the default route missing after reboot?
• Network default gateway address cannot be added