As much as locks are critical for a host of facets in your life, from your house and car, to even your office building, people tend to take their locks and keys for granted as long as their locks are apparently working. However, this nonchalance about their functionality is what eventually lead to situations that would need the expertise of a locksmith. Emergencies can never be scheduled. Thus, while you think that you can easily reach a locksmith when this happens to you, it is not the case if your locks act up after hours.
Waterproof and water-resistant locks aren't quite the same thing. Consider your smartphone. Some manufacturers claim that their products are waterproof, and while it might have a sealed body that means the phone won't be damaged if it's accidentally submerged in water, it's not as though it could be left underwater indefinitely without problems. A water-resistant phone can still work when exposed to water, but it might not survive a full immersion in water.