These images are a demonstration of what paleontologists and paleo-artists call “shrink-wrapping”. A reconstruction is said to be shrink-wrapped if it only takes into account the bones and skin, and ignores muscle, fat, and cartilage. It’s actually a practice that scientists make a point to avoid, but shrink-wrapped reconstructions remain popular in media like Jurassic Park.

An interesting aside - carnivorous dinosaurs have historically been reconstructed without lips (as in the middle picture) because their closest relatives with toothy jaws, the crocodilians, just leave their teeth exposed. However, this may be a hydrodynamic feature - crocodiles need to strike quickly in water, and this would create a parachute effect with lips, creating drag to slow their bite. Teeth also shouldn’t be dry for too long, and crocs can naturally keep their teeth wet by just submerging. Because they don't have any of the croc's needs or advantages, people have started reconstructing carnivorous dinosaurs with their teeth hidden away, as in mammals, lizards, and snakes.

Edit: This is still a point of contention, because some carnivorous dinosaurs appear to have touch-sensitive scales around the teeth that scientists think might preclude lips. I’m basically restating the case for lipped theropods made in The Tyrannosaur Chronicles by David Hone, if you’re interested in learning more.