I went in to the theme code to troubleshoot it and actually found out it is a part of theme contact form styles which is performed by the following codes.
if( isset($atts['style']) && $atts['style'] == 'style2' ) : ?>
#contact-form-<!--?php echo esc_attr( $atts['id'] ); ?--> label {
display: none;
}
#contact-form-<!--?php echo esc_attr( $atts['id'] ); ?-->.contact-form input,
#contact-form-<!--?php echo esc_attr( $atts['id'] ); ?-->.contact-form textarea {
text-align: left;
border-radius: 25px;
padding: 29px 30px;
border-width: 0px;
}