Pressurized with what? Oxygen? BOOM! Only small chunks remain. What inert gas would it be pressurized with?
Helium. The smaller spherical tanks might be for Hydrazine or other hypergolic/binary propellants for RCS, but often it's a helium tank used to pressurize the fuel and drive it out of it's tank and fill the growing void in the tank to maintain pressure, and it's structural integrity too.
The high thrust of takeoff can't be managed in large rockets simply by a helium pressurization system to drive the oxidizer and fuel to the combustion chamber and rocket nozzle, they use turbopumps for that of course, but they still use helium pressurization to back-fill the tanks etc. keep everything moving in the right direction and whatnot.
The smaller RCS systems, and lower powered orbital maneuvering thrusters, and station-keeping might be entirely pressure-fed with helium.