Why are Serializable and Parcelable extras not kept in a PendingIntent?

Question

In order to create a precise alert with some information, I tried to pass a simple POJO through the extra data of an Intent, nested into a PendingIntent. I gave this latter to the AlertManager service class.

I tried to implement Serializable, I ended up with nulls when receiving the PendingIntent. I then tried to implement Parcelable and adding all the needed methods and members, still ending in getting nulls.

I succeeded by doing a work-around, consisting in copying the ParcelableUtil class found here and putting the marshalled data as a byte array. This worked, for some reason.

private void scheduleAlert(Element element) {
    Intent intent = new Intent(this.context, ReminderReceiver.class);
    // Serializes the element and puts it into the extra intent data.
    
    // ---- TRY 1 (tried with Serializable & Parcelable)
    intent.putExtra("extra key", element);
    // --------
    
    // ---- TRY 2
    Bundle extras = new Bundle();
    extras.putSerializable("extra key", element);
    intent.putExtras(extras);
    // --------
    
    // ---- TRY 3
    Bundle extras = new Bundle();
    bundle.putParcelable("extra key", element);
    intent.putExtras(extras);
    // --------
    
    // ---- WORKAROUND
    byte[] bytes = ParcelableUtil.marshall(element);
    intent.putExtra("extra key", bytes);
    // --------
    
    PendingIntent pendingIntent = PendingIntent.getBroadcast(this.context, element.getRequestCode(), intent, 0);
    AlarmManager alarmManager = (AlarmManager) this.context.getSystemService(Context.ALARM_SERVICE);
    
    long reminderPeriodMillis = element.getReminderPeriod() * 1000;
    long firstAlarmMillis = SystemClock.elapsedRealtime() + reminderPeriodMillis;
    
    // Creates the alarm.
    alarmManager.setExactAndAllowWhileIdle(AlarmManager.ELAPSED_REALTIME_WAKEUP, firstAlarmMillis, pendingIntent);
}

The Element class can be found bellow.

public class Element implements Serializable, Parcelable {

    private static final long serialVersionUID = 1L;

    private String title;
    private int reminderPeriod;
    private int requestCode;

    public Element(String title, int reminderPeriod, int requestCode) {
        this.title = title;
        this.reminderPeriod = reminderPeriod;
        this.requestCode = requestCode;
    }

    public Element(Parcel in) {
        this.title = in.readString();
        this.reminderPeriod = in.readInt();
        this.requestCode = in.readInt();
    }

    public static final Creator<Element> CREATOR = new Creator<Element>() {
        @Override
        public Element createFromParcel(Parcel source) {
            return new Element(source);
        }

        @Override
        public Element[] newArray(int size) {
            return new Element[size];
        }
    };

    @Override
    public int describeContents() {
        return 0;
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeString(this.title);
        dest.writeInt(this.reminderPeriod);
        dest.writeInt(this.requestCode);
    }

    public String getTitle() {
        return this.title;
    }

    public int getReminderPeriod() {
        return this.reminderPeriod;
    }

    public int getRequestCode() {
        return this.requestCode;
    }
}

And the code receiving the alarm:

@Override
public void onReceive(Context context, Intent intent) {
    // TRY 1 (with Serializable)
    Element element = (Element) intent.getSerializableExtra("extra key");
    // --------

    // TRY 1 (with Parcelable)
    Element element = (Element) intent.getParcelableExtra("extra key");
    // --------

    // TRY 2
    Bundle extras = intent.getExtras();
    Element element = (Element) extras.getSerializable("extra key");
    // --------

    // TRY 3
    Bundle extras = intent.getExtras();
    Element element = extras.getParcelable("extra key");
    // --------

    // ---- WORKAROUND
    Bundle bundle = intent.getExtras();
    Parcel parcelIn = ParcelableUtil.unmarshall(bundle.getByteArray("extra key"));
    Element element = new Element(parcelIn);
    // --------

    // [...]
}

TL;DR: Why is my data not kept as Parceled and Serialized extra, but kept if passed as an extra byte array?