First html helper generates client-side validation attributes, while the second one doesn't

Question

Let's say I have this model:

public class Person
{
    public bool IsApproved { get; set; }
}

And whis this codes, I am trying to render input with check type:

@Html.CheckBoxFor(x => x.IsApproved)
@Html.CheckBox("IsApproved")

But, the results are different:

// CheckBoxFor result
<input data-val="true" data-val-required="The IsApproved field is required." id="IsApproved" name="IsApproved" type="checkbox" value="true">
<input name="IsApproved" type="hidden" value="false">

// CheckBox result
<input id="IsApproved" name="IsApproved" type="checkbox" value="true">
<input name="IsApproved" type="hidden" value="false">

How and why, the first one generates attributes for client-side validation, while the other didn't?

Update:

After swapping the order of @Html.CheckBoxFor and @Html.CheckBox, the order of markup elements didn't change.