Helium is an inert and near perfect gas allowing for more efficiency in pressurized storage systems.
Great points
Just for fun…
Also He monatomic gas is 4 grams per mole vs 28 for N2. So 7x as heavy to pressurize the same, using N2. A full 80 cu ft scuba tank full of air (mostly N2) weighs an extra 5.7 pounds ( 3000 psi vs 14.7 ) . For pressurizing tanks and/or using it as reaction gas I am guessing you would use probably the order of hundreds of pounds of N2 or more.
Helium costs up to $70 / lb. Cost to launch a pound to space station tens of thousands of dollars per pound on non-reusable vehicles. So hundreds of thousands to millions of dollars or more cheaper per launch.