Though there is much prehistorical evidence lacking to back up both my view and this one I believe plants evolved to become carnivorous. It's a whole mechanism that relies on prey and symbiotic relationships with bacterias in some instances. The probability that a mechanism as complex as the one we see today, would have appeared with the intent of deriving nutrients from bugs by luring, capturing, killing, digesting, and assimilating is very very very very slim if not unheard of.
Different plants in different parts of the world evolved similar mechanisms (Sarracenia, Nepenthes, Heliamphora). These mechanisms all worked in the same manner but we can see very clearly that there is not just one proper form for a mechanism but in this case, 3 that we know of. There are even different specimens within the same genus suggesting that these plants have evolved from 1 distant common ancestor.
There is evidence that VFTs evolved from Drosera. If two specimen can be so physically different yet come to be more closely related then we could imagine, it may be that Drosera's ancestor (or any other CP) was just as much different, even possibly non carnivorous (though there is no data or proof to back this up).
Plants dont just appear with a plan on how they're going to survive. It's a battle of the fittest in the environment that they end up being set in and the ones that made it through the challenge of nutrient poor soil were the ones that had genetic mutations which allowed them to collect nutrients from insects in their own environment through their leaves. How many mutations it took to get to the plants we know today is a mystery but I would love to have this riddle solved sometime in my lifetime. I just simply do not agree with the theory of creationism.