Originally Posted by Wraith Rider
There's reason to be concerned about going out of the door at all. But street riding is not that scarry. Only the needed skills differ slightly from the dirt riding skills. Navigating traffic instead of terrain for example.
Trees, rocks, cliffs, etc. don't generally swerve into one's path, whether accidentally, distractedly, or purposely. Trees, dirt, sand, and many other offroad obstacles also have a bit more give to them than vehicles, curbs, buildings, walls, dividers, guard-rails, etc. The offroad obstacles also can't typically gang up and run you over if the first one didn't finish the job. The inertia involved in offroad crashes is probably considerably less, on average.
Closing speed on dirt is generally simply how fast the rider is going, and most dirt riders that gear up wear considerably more/better impact-dispersing gear than most street riders wear when they "gear up". I get strange looks wearing chest or back protection on the street. I get strange looks from wearing armored pants for riding pavement, or even armored full-finger gloves. Even many dirt riders give in to the peer pressure when riding pavement, and don't gear up to the same extent that they do on dirt.
Riding dirt well also develops the skills that help handle a bike when situations, including traction, go to crap. A skilled dirt rider doesn't have to as-consciously think about controlling the bike.
This does not mean that a dirt rider should just start riding street without developing some street skills though. The dirt skills are PART of an excellent base to build from. On street, I think that STRATEGY plays more a part of safely navigating traffic if the bike-handling skills have already been developed in dirt. A dirt-skilled rider can focus more of their brain function and attention on strategy, rather than having to ALSO focus on controlling the bike when it's at the limit, or possibly even beyond. For similar reasons, track days/schools can be good too, but the skills developed there would probably not translate as well as dirt skills to everyday traffic situations, with the lower speeds and possibly-wide variations in traction encountered on public roads.