Cheap tents or tarps or no tent at all are fine in good weather. I've slept in just a bag and light bivy sack (BD Winter Bivy) on snow (on my two pads, of course). If I was industrious enough, I could just take a shovel (I do anyway) and build an igloo in winter, but a tent is far easier to set up.

Where the difference comes in is in bad weather. I have a five pole winter tent with full rain fly and vestibule. When staked down, I think it could withstand almost anything except hurricane force winds. I've spent some time in pouring rain in a Sierra Design Flashlight; not the ideal tent for rain (no vestiblule), but waterproof.

I've read too many accounts of leaking tents, snapped poles and torn flys to put much faith in cheap tents. Car camping? Sure, why not, you've got a bailout shelter (your car) nearby, so if the tent comes apart, you aren't going to die from exposure.