There’s a whole lot of testing done for various reasons before doing anything in humans. And yeah, this is one of the many, many inappropriate stories on HN as it tries to morph into a less technical, more oppositional forum.
It is also a matter of risk management: assuming that two doses always create stronger immunity than one dose, it's better to do a successful Phase 3 trial with two doses and "miss out" on getting approval for a one-dose course, rather than aim for a one-shot vaccine, and risk the response being too small to get any approval at all.
Also, if the drug is successful in the market, Glaxo can do another trial to show that 1 dose is not inferior to 2 doses, and get a patent extension for the new formulation.
If you get shingles you wont be doing any hacking for awhile, so health issues are relevant. There are many HN topics on Coronavirus and other health issues. Someone recently asked how to deal with depression and no one challenged that.