Your reputation is only as good as the people who know it. Most HR will not have heard of you (unless you are a high-profile leader in your field) and hence the desire for a rubber stamp from a brand company. It's the same reason many people desire Ivy League education, not for the learning, but the brand name that will make entry to most jobs a lot easier (as HR/Company assume certain level of quality/competency/work-ethic/etc has been met).
Which again, circles back to reputation building. Somebody, as you say, has to be impressed/like you enough to make the effort of pushing your information through the ranks to get hired. If you know the person from some other context, it's possible. If you're another resume from the stack, it's much more difficult to get that attention from anyone-HR, engineers, managers-in the company.
