Why does the radio group component not use standard markup? (e.g. fieldset, input type="radio")

[gurpreetatwal]

Apologies in advance if this is a silly question, but why do the radio group components use a div and button and add form functionality instead of using the builtin HTML form elements?

e.g.

<RadioGroup.Root> -> div role="radiogroup"
  <RadioGroup.Item> -> button role="radio"
  <RadioGrop.Input> -> input type="hidden"

as opposed to

<fieldset>
   <legend> <!-- could even make this a sr-only if styling is the issue -->
   <input type="radio">