For the same reason that in WP you do
if (have_posts()) {
while(have_posts()) {
the_post();
}
}
What if you want to do something outside the while loop but only if there are rows? What if you want to do something different if there are not rows?
if (have_rows('field')) {
// do something here before the loop
while(have_rows('field')) {
the_row();
}
// do something here after the loop
} else {
// do something different if there are not rows
}
Just like you can skip if (have_posts()) you can skip if(have_rows()) if you’re sure you don’t care what happens if there are none.
