Seems the greatest value of video/photo/witness evidence would be to speak for you when you can't speak for yourself; next best to corroborate your version. Multiply that value in case of repeat offenders (or revenge). It'd be the extremely rare traffic officer (among those who are diligent and honest, at least) who would insist that during the time from incident until her or his response at the scene you were somehow able to fabricate a false video with only your helmet cam or phone cam. Of course most people (including license revocation hearing judges) believe what they can plainly see. Leave it to the driver to attempt to concoct a plausible explanation of how their vehicle and body shows up on the video (how else would you have obtained it--pre-accident surveillance?), perhaps coupled with paint transfer marks or other compatible physical indicia.

One concern in small geographic areas--such as where the same officer shows up, and again dismisses the complaint as if s/he were the judge or prosecutor--might be protecting local residents or the officers' friends/relatives/business dealings.

One other point I think was overstated earlier: laws against use of intersection camera evidence I personally suspect (but haven't researched) wouldn't prohibit video use in investigation for possible criminal assault/battery or possible revocation of license privileges, and they're used regularly to identify perpetrators of various types of crimes as well as identify potential witnesses (e.g., license plates of potential witnesses in other vehicles). The correct analysis of how it might be useful to you of depends on your state and/or your local traffic jurisdictions.