There are times when matching the hatch can be important. Watch BassResource's video on fishing a Spook and you see that what he is using on schooling fish is close enough to the bait to get bit. When it comes to plastics I am not sure that bass know or care what it looks like. They are programmed to eat and are opportunists. When something comes by that looks and moves like prey they just react. Why a Rage bait works well sometimes, and at others a Netbait, or Zoom, or one of a thousand other manufacturers works better is a function of the mood of the fish IMO. Sometimes a very slow presentation works well, other times something faster is better; sometimes a big profile is good, other times smaller is better; sometimes a subtle green or brown is better; sometimes bright and gaudy, or dark is the better choice. The real challenge is to identify what works on a given day. For me it is just that simple, and that complex.
I was soundly out-fished by a friend last week from the back of my boat. We had maybe the best day of big fish either of us has ever had. I caught three very nice fish, broke off another and lost another at the boat. He caught seven, two of which were legitimate pigs. I was using jigs, brushhogs, and a variety of other plastics including a Trickworm on a shakyhead that produced my biggest fish. He was using RI beavers. All the good fish were caught in 15-20 feet of slightly stained water. The difference was not the bait or the color IMO. He was using a 1/2 oz tungsten weight and I was too stubborn to use that heavy because the rocks were hungry and I did not want to lose my tackle. I used 5/16 and 3/8 oz and did not lose much tackle, but the faster rate of fall and keeping it on the bottom was the secret of the day I believe.
I understand that I have not really answered the question of why fish bite plastic worms, or Senkos, or plastics in general. I take for granted that most of the time they will. For me the question is where are the fish and what do they want today. Once you can answer that question you can start to refine your presentation to target the better fish, unless you are a little dense like I sometimes am and not paying close attention to details.