If I showed you a list of non-Bitcoin-accepting merchants picked at random, you would almost certainly have the same reaction: you would not trust most of them, because they are all too tiny and you have never heard of them.
You have to realize that the web is a long-tail ecosystem. There are tons of small merchants you have never heard of, while the biggest ones (Amazon, Newegg, etc) are just a few and represent <1%. What you call a "reputable" merchant exclude 99% of all merchants. Plus, the most reputable/biggest merchants will probably be the last ones to adopt Bitcoin (the bigger you are, the less likely you are to adopt a disruptive technology).
