HTML has a handy
label element that allows to associate text with a form control and in graphical user agents allows the user to give focus (or execute an action) on such a control by invoking the label with a pointing device, e.g. the mouse or a finger.
Not using it basically means that the user has to hit a tiny target of often just 16×16 px² which, as Fitts' law tells us, is worse than hitting a target of 300×16 px².
This is basically a conceptual duplicate of my older feature-request: Could checkboxes such as “Notify” get an HTML label tag?