I am following the Apple tutorial to learn how to make iOS apps. This is the link: https://developer.apple.com/tutorials/develop-in-swift/design-an-interface

In the app OnboardingFlow, I am trying to set the background of FeaturesPage in the preview to a gradient with colors that I have defined in my Assets folder. The background shows up behind the text but not behind the FeatureCards I’ve defined.

This is my FeatureCard:

//
//  FeatureCard.swift
//  OnboardingFlow
//
//

import SwiftUI

struct FeatureCard: View {
    let iconName: String
    let description: String
    
    var body: some View {
        HStack {
            Image(systemName: iconName)
                .font(.largeTitle)
                .foregroundColor(.white)
                .frame(width: 50)
                .padding(.trailing, 15)
            
            Text(description)
                .foregroundColor(.white)
            
            Spacer()
                
        }
        .padding()
        .background(.tint, in: RoundedRectangle(cornerRadius: 12.0))
        .frame(width: 350)
    }
}

#Preview {
    FeatureCard(iconName: "person.2.crop.square.stack.fill", description: "A multiline description about a feature with the image on the left.")
}

This is my FeaturesPage:

//
//  FeaturesPage.swift
//  OnboardingFlow
//
//

import SwiftUI

struct FeaturesPage: View {
    var body: some View {
        Text("Features")
            .font(.title)
            .fontWeight(.semibold)
        FeatureCard(iconName: "person.2.crop.square.stack.fill", description: "A multiline description about a feature paired with the image on the left.")
        FeatureCard(iconName: "quote.bubble.fill", description: "A short summary.")
    }
}

#Preview {
    FeaturesPage()
        .background(Gradient(colors: [.white, .gray]))
}

Why is the background I apply in the preview not showing up across my whole FeaturesPage View?