Question about UpdateInstaller

Hello!
Why Backup existing system files option (on the Update Installer GUI) is not selected by default?
Why Backup existing system files option (on the Update Installer GUI) is not selected by default?
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backup=Enabled
[Installation]
backup=Disabled Backup
updatercerts=Enabled Root Certificates
instie7=Disabled Internet Explorer 7
instie8=Enabled Internet Explorer 8
instie9=Disabled Internet Explorer 9
instie10=Disabled Internet Explorer 10
updatecpp=Enabled Visual C++ Runtimes
updatedx=Disabled Microsoft DirectX
instmssl=Disabled Microsoft Silverlight
updatewmp=Enabled Windows Media Player 11 (XP only)
instdotnet35=Disabled .NET Framework 3.5 SP1
instdotnet4=Disabled .NET Framework 4.0 / 4.5
instpsh=Disabled Powershell (depends .NET Framework)
instwmf=Disabled Windows Management Framework (depends .NET Framework)
instmsse=Disabled Microsoft Security Essentials
updatetsc=Enabled Windows Remote Desktop
instofc=Disabled Office File Converter (Office 2003)
instofv=Disabled Office File Validation (Office 2003 & 2007)
all=Disabled Install all Updates (even those, which are already installed)
excludestatics=Disabled Don't install the statical defined updates
skipdynamic=Disabled Just install the statical defined updates
[Control]
verify=Enabled Check the Hashes of the files before installing
autoreboot=Disabled Reboot computer after update and relaunch update process automatically until all updates are installed
shutdown=Disabled Power off the computer, after the update completed
[Messaging]
showlog=Disabled Show the logfile after update
boco wrote:Also note that Backup does only concern Windows XP and maybe Office. On modern OS Backup cannot be disabled.