system
Given the following post, respond as if you're commenting on Reddit:
human
[Halo] Why have the UNSC not incorperated covie tech into their ground vehicles. 

For instance, why haven't they made a hover hog yet. Also why no energy blades for melee weapons. Why are they still using metal knives?
gpt
In direct answer to your question, the UNSC has a reliable tested and true set of equipment and in the midst of a total war scenario it is much more cost and *life* effective to use comparitively cheap and simple to produce technologies. Hover-hogs and Energy Knives are not going to radically improve ground battle performance, coupled with the depressing fact that almost all ground victories are followed by an orbital defeat further enforce staying with what we know instead of using experimental technologies. 

The UNSC has been in a state of total warfare against the Covenant hegemony for 27 years, during that time various technologies have been co-opted, adapted and improved by our scientists and technicians. The most notable example of this would without a doubt be the personal energy shield technology famously employed by Spartan 2 assets, intriguingly this was derived from the energy shield gauntlets employed by Kig-Yar auxilliaries as opposed to the energy harness employed by Sangheilli infantry. A similar technology was concurrently developed by the beta-5 division of ONI, known as the "bubble shield" which is all but invunerable to any munitions commonly employed in ground combat with the covenant. 

More recently since hostilities have ceased after the dissolution of the Covenant hegemony, and the aquisition of Forerunner Huragok, colliquially known as engineers, the UNSC has been able to provide shielding to Charon class light frigates as well as the new UNSC flagship - Infinity. In addition 2 single occupancy vehicles have energy shields equipped, the YGGADRASIL Mk. 9 Armour Defence System AKA the "Mantis", and the F-41 Broadsword Space Superiority Interceptor. 

However energy shielding is only one of the many technologies the Covenant possessed which the UNSC did not. We have since discovered that the aforementioned Huragok in conjunction with the San Shy'uum produced and maintained almost all technology employed by the other Covenant species. The destruction of high charity heralded the extinction of the San Shy'uum, and any Huragok not destroyed have disappeared from the remaining species' grasp, this turn of events has shown us how the remaining Covenant species have extremely little to no understanding of how their own technology works. (This fact *will* be exploited for human benefit.) Further conjecture suggests that almost all Covenant technology is adapted and modified Forerunner technology, so now the UNSC has a population of Huragok (Both Ex-Covenant *and* original Forerunner) we will be able to apply technologies used by the Covenant into both military and civilian life whilst making sure to avoid the pitfall of the Covenant and learning for ourselves what the Huragok are actually doing.