Why does the majority of hydrogen atoms not contain a neutron?

Some hydrogen atoms do have a neutron, even naturally occurring. The great majority do not. Most likely the most common form of any element is the most stable form, while other forms might even be radioactive so they don’t last, or at least are less likely to be formed in the first place.

during the early formation of the universe, protons were abundant. when the universe cooled, each proton married and electron to form a hydrogen atom. but, alas, there were other particles formed and some of the proton had an affair with neutrons before marrying the electron. so, a small percentage of hydrogens had a neutron. its only a small amount, probably less than 1% but not sure on the value. Hydrogens contain either 0 protons (99%), 1 neutron (0.90%) or 2 neutrons (0.01%).

sorry bro, i know you mean well but your answer is wrong and butchered.

there are three major types of hydrogen atoms (isotopes), 1st is Hydrogen with 1proton and 1 electron, 2nd is Deuterium with 1 neutron, 1proton, 1 electron, 3rd tritium with 2neutrons, 1 proton, 1electron,..these are naturally occurring isotopes, others may have been synthesized in labs