Spacesuits have actually changed enormously. The earliest spacesuits were essentially just airtight versions of the flight suits pilots wore. In 1965 cosmonaut Alexei Leonov almost became stranded in space during the first spacewalk, when his spacesuit ballooned out so much from its internal pressure that he couldn’t move or operate the airlock door.
The A7L suits developed for the Apollo missions used constant-volume joints to avoid this problem and added a self-contained air recycling unit and 100m of piping to pump cooling water around the suit. The suits were custom tailored and each astronaut needed three suits (for training, flight and a spare) costing around half a million dollars each.
The EMU and Russian Orlan suits, currently used on the International Space Station, are modular to keep costs down and because they are only used in microgravity, they can be much heavier. These suits have a rigid upper torso, which offers better protection and comfort. For future missions to Mars, NASA is developing the Z-series suits that have rigid joints with titanium bearings to allow the greatest flexibility. These are the first spacesuits that allow the wearer to touch their toes, and they also have a built-in airlock.