Just to note, the linked story is about David Mayman of Jetpack Aviation in California, while the other stories you mentioned are (British) Richard Browning of

Just to note, the linked story is about David Mayman of Jetpack Aviation in California, while the other stories you mentioned are (British) Richard Browning of Gravity Industries - the one recognisable by its wrist-mounted supplementary engines. So there are at least a couple of competing inventions. Sure, there isn't a killer app for jet packs at the moment, or perhaps ever. They were enabled by miniature-scale turbine engines being developed for other purposes. But you never know - some innovation in control systems, or them turning out to be just perfect for some obscure emergency/military task, they might find a niche beyond stunts and tethered tourist experiences.