Because only the rich can afford cheap batteries..... A good quality deep cycle lead acid battery will cost between $50 and $200 and, if properly maintained, will give you at least 150 deep discharge cycles.
What is the boiling point of oxygen? a. 100 degrees C c. -57 degrees C b. 8 degrees C d. -183 degrees C.
For Hydrogen, the boiling point is -253 degrees Celsius; for Mercury it is 357 degrees Celsius, and for Iron it is 2,750 degrees Celsius. From these numbers you can see that at room temperature (and indeed for nearly any temperature found on Earth) Hydrogen is a gas, Mercury is a liquid, and Iron is a solid.