The genetics behind that relentless appetite
Labradors have a well-documented tendency toward food-seeking behaviour, and some of that really is genetic — a meaningful proportion of Labradors carry a variation in a gene involved in appetite regulation, which can make them feel hungry more often than dogs without it.
That's not an excuse to free-feed or over-treat; if anything it's a reason to be stricter about measured portions, since a Labrador's hunger cues are a poor guide to how much food they actually need.
This is also why weight checks matter more for Labradors than for breeds without this tendency — running a hands-on body condition check monthly, rather than relying on visual impression, catches gradual weight gain before it becomes a harder problem to reverse.