Last sunday I was fishing a row of rocks in a lake with a small crankbait, and I pulled in a few sunfish and little bass. But I kept at it, know that the area was good and finally got a 5 lb smallmouth.
There are a couple ways to look at this. One is if its just bluegill you a getting picked at, then there may not be a bass *right* there. But, a fish is a fish., A bass is just a big bluegill, and a lot of times if you are getting bluegill the bass are so close by you really just need to keep covering the area, weave in, weave out, they wont be far.
One thing that is true in the fish world; its a competition. Sometimes, if there is a lone fish there with no competition and it sees a lure, it has the luxury of taking its time when "deciding" whether it should strike. But throw other fish in there competing for that lure, even bluegill or little bitty bream, and that will inspire the competitive instinct to bite. Even if the lure presentation looks like garbage, the bass will go from feigning indifference to aggressively exploding on that lure first.