[WPF] StaticResource not applied inside DataTemplate but works outside

xaml
<Page
    x:Class="Wpf.Ui.Gallery.Views.Pages.Text.NumberBoxPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:controls="clr-namespace:Wpf.Ui.Gallery.Controls"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:helpers="clr-namespace:Wpf.Ui.Gallery.Helpers"
    xmlns:local="clr-namespace:Wpf.Ui.Gallery.Views.Pages.Text"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:system="clr-namespace:System;assembly=System.Runtime"
    xmlns:ui="http://schemas.lepo.co/wpfui/2022/xaml"
    Title="NumberBoxPage"
    controls:PageControlDocumentation.DocumentationType="{x:Type ui:NumberBox}"
    d:DataContext="{d:DesignInstance local:NumberBoxPage,
                                     IsDesignTimeCreatable=False}"
    d:DesignHeight="450"
    d:DesignWidth="800"
    ui:Design.Background="{DynamicResource ApplicationBackgroundBrush}"
    ui:Design.Foreground="{DynamicResource TextFillColorPrimaryBrush}"
    Foreground="{DynamicResource TextFillColorPrimaryBrush}"
    mc:Ignorable="d">
    <Page.Resources>
        <helpers:NumberFormatter x:Key="NumberFormatter" />
        <DataTemplate x:Key="TestDataTemplate">
            <controls:ControlExample
                Margin="0"
                HeaderText="WPF UI NumberBox."
                XamlCode="&lt;ui:NumberBox PlaceholderText=&quot;Enter your age&quot; /&gt;">
                <ui:NumberBox NumberFormatter="{StaticResource NumberFormatter}" PlaceholderText="Enter your age" />
            </controls:ControlExample>
        </DataTemplate>
    </Page.Resources>

    <StackPanel Margin="0,0,0,24">
        <ContentControl ContentTemplate="{StaticResource TestDataTemplate}" />
        <controls:ControlExample
            Margin="0"
            HeaderText="WPF UI NumberBox."
            XamlCode="&lt;ui:NumberBox PlaceholderText=&quot;Enter your age&quot; /&gt;">
            <ui:NumberBox NumberFormatter="{StaticResource NumberFormatter}" PlaceholderText="Enter your age" />
        </controls:ControlExample>
    </StackPanel>
</Page>