HTML and Forms helpers

[eluser]_TTT_[/eluser]
CI has HTML and FORMS helpers for what ?
I cant understed why those functions
For example

CI

echo form_open('email/send');
echo form_input('username', 'Alex');
echo form_close($string);

in Clear HTML

<form method="post" action="post/send">
<input type="text" name="username" value="Alex" />
</form>

what is reason ?