Yeah, some bicycle tires are light because the sidewalls are thinner than those on other tires.
Don’t want to single out Continental, as the GP4000s are my go-to tires (they’re pretty popular among a lot of road bicyclists) for longevity, rideability, and yes, weight. (Psst! Wait for them to go on sale online at places like ProBikeKit or other UK shops for about $35/each.) But I finally had one of the sidewalls go out on me on one of these tires. Fortunately, I was able to come to a quick stop before I lost control of the bike.
As a rule–while you’re riding, try to imagine the worst possible thing that could happen and be prepared for it. That car could hook a right right in front of you (even without indicating his intention to turn with a turn signal!), your crank arm could break, your chain could snap, you could hit a piece of glass or a thorn in the road, a coyote could run out in front of you, those School of the Arts kids waiting at the intersection to cross the street might actually walk backwards into the middle of the street without looking, and so on. So get ready to hit those brakes, take a fall, grab your bars, etc. (I try to keep my teeth clenched lest I wreck and bite off my tongue or lip or something.)
The life you save may be your own.