Giant Spiders

Okay. Spiders are brilliant, if a little creepy. But what if we had giant spiders? I'm not talking chihuahua-sized, I mean big. For a reference, imagine a car. Now imagine this car being ripped into multiple pieces by a spider. Then imagine that spider being consumed by a colossal monstrosity of an arachnid. I'm talking BIG.
I'm not even going to mention the problems with the thing actually existing (it couldn't, which I assumed would be fairly obvious, but hey, I always overestimate the intelligence of peasants), but rather I shall talk about the implications of such a gargantuan beast.
Let's start with a slightly smaller spider, say the size of a cat. This thing seems like a good idea (I'm lying), but think about it. Normal spiders eat flies, so the logical follow up to that is that cat-sized spiders would eat roast dinners. And they would stop at nothing to get at them; imagine the scene, a nice roast dinner, then all of a sudden your window doesn't exist anymore. You go to check out the remaining mess of what was previously your window and hear a scratching sound. You swivel round at about a billion miles per hour and spot a black splodge, which is making off with your lovely snack.
You pack your bags to embark on a stupidly pointless quest on a journey to discover how and why your delicious supplement was dragged away. After many days on this quest you realise it was a stupid idea and turn to go home. As you swivel round you are pounced upon and eaten by a spider the size of a house. As you are slowly digested you realise it was a stupid idea to imagine this scene, as you are now dead and you knew that you would die from the start and you are just a bit silly for thinking that thinking about giant spiders was a good idea.
Now that we have gone over the problems with cat sized spiders, let's go over the problems with spiders the size of galaxies. A spider this size would be rather messy and rather than hunting flies, it would probably go around hunting spaceworms and that doesn't benefit anyone.
So giant spiders.
Prolonged contact with peasants is dangerous and could bring up previous heart conditions that have previously gone unnoticed. So goodbye.