I prefer to separate my appSettings and connectionStrings elements out of my web.config and keep them in separate config files. My customized web.config file replaces the elements with the following:

<appSettings configSource="config\appSettings.config" />
<connectionStrings configSource="config\connectionStrings.config" />

However, I discovered that for some reason, when building from source, these are being stripped out and replaced in my modi

This is defined in web.Template.Debug.config:

<appSettings xdt:Transform="Remove" xdt:Locator="Condition(@configSource != '')" />
<appSettings xdt:Transform="InsertIfMissing">
  <add key="umbracoConfigurationStatus" value="" />
  <add key="umbracoReservedUrls" value="~/config/splashes/booting.aspx,~/install/default.aspx,~/config/splashes/noNodes.aspx,~/VSEnterpriseHelper.axd" />
  <add key="umbracoReservedPaths" value="~/umbraco,~/install/" />
  <add key="umbracoPath" value="~/umbraco" />
  <add key="umbracoHideTopLevelNodeFromPath" value="true" />
  <add key="umbracoUseDirectoryUrls" value="true" />
  <add key="umbracoTimeOutInMinutes" value="20" />
  <add key="umbracoDefaultUILanguage" value="en" />
  <add key="umbracoUseSSL" value="false" />
  <add key="ValidationSettings:UnobtrusiveValidationMode" value="None" />
  <add key="webpages:Enabled" value="false" />
  <add key="enableSimpleMembership" value="false" />
  <add key="autoFormsAuthentication" value="false" />
  <add key="log4net.Config" value="config\log4net.config" />
  <add key="owin:appStartup" value="UmbracoDefaultOwinStartup" xdt:Transform="InsertIfMissing" xdt:Locator="Match(key)"  />
</appSettings>

<connectionStrings xdt:Transform="Remove" xdt:Locator="Condition(@configSource != '')" />
<connectionStrings xdt:Transform="InsertIfMissing">
  <remove name="umbracoDbDSN" />
  <add name="umbracoDbDSN" connectionString="" providerName="" />
</connectionStrings>

My questions is -- WHY?

What is the purpose of explicitly replacing the appSettings and connectionStrings elements with boilerplate code just because they contain a configSource redirect??

Note:
For reference and clarification, this all occurs in the first place because of this section in Umbraco.Web.UI.csproj:

<Target Name="BeforeBuild">
  <!-- Create web.config file from Template if it doesn't exist -->
  <Copy SourceFiles="$(ProjectDir)web.Template.config" DestinationFiles="$(ProjectDir)Web.config" OverwriteReadOnlyFiles="true" SkipUnchangedFiles="false" Condition="!Exists('$(ProjectDir)Web.config')" />
  <!-- Transform the local Web.config file in Visual Studio -->
  <TransformXml Source="$(ProjectDir)Web.config" Transform="$(ProjectDir)web.Template.$(Configuration).config" Destination="$(ProjectDir)Web.$(Configuration).config.transformed" Condition="$(BuildingInsideVisualStudio) == true" />
  <!-- Always transform the Template file when not in VS (ie: build.bat) -->
  <TransformXml Source="$(ProjectDir)Web.Template.config" Transform="$(ProjectDir)web.Template.$(Configuration).config" Destination="Web.$(Configuration).config.transformed" Condition="$(BuildingInsideVisualStudio) != true" />
  <!-- Only runs if the Belle build folder doesn't yet exist -->
  <CallTarget Targets="BelleBuild" Condition="!Exists('$(ProjectDir)\..\Umbraco.Web.UI.Client\build')" />
</Target>
<Target Name="AfterBuild">
  <Copy SourceFiles="$(ProjectDir)Web.$(Configuration).config.transformed" DestinationFiles="$(ProjectDir)Web.config" OverwriteReadOnlyFiles="true" SkipUnchangedFiles="false" Condition="$(BuildingInsideVisualStudio) == true" />
</Target>