There are human portable rocket packs which do work, albeit to a fairly limited extent.
The minimum terminal velocity in a stable 'belly to earth' position is about 50 metres per second so even at a fairly modest 10 g that is only about 5 seconds to slow down to a stop. So it's certainly not impossible.
However parachutes work pretty well at what they do. They are very simple and reliable and light and compact enough that they don't encumber the wearer much and you can carry a second one as a reserve which further improves their reliability. They don't require much maintenance beyond proper storage and for a safety-critical item they aren't really that expensive.
Equally importantly they are pretty easy to use. If you jumped out of a plane wearing one you would have a pretty good chance of surviving, even with minimal instruction. Obviously a moderate amount of training is desirable for dealing with emergencies and reducing the risk of injury on landing but even so there are a significant number of competent amateur parachutists.
Also once a parachute has deployed successfully there is little left to go mechanically wrong
On the other hand rocket packs require significant skill to fly at all they usually launch from a standing position and the pilot stays upright throughout the flight whereas free-fall parachutes are usually deployed from a belly down spreadeagled position which is inherently stable and works nicely with a backpack type parachute harness.
With a limited fuel supply you need to be able to time the deployment of thrust pretty accurately so you have a fairly narrow window to get it right, as opposed to a parachute where any altitude above the minimum safe deployment is basically fine (obviously jumping from very high altitudes has a whole separate set of problems).
Equally a rocket pack is mechanically complex, heavy and bulky and most rockets use fuel which is hazardous and requires special handling.
So really you are talking about replacing a simple, inexpensive and proven system with something which has never really got beyond the prototype stage, doesn't offer any obvious advantages and has several inherent drawbacks.