To continue moving "straight down" its angular velocity would need to be constant, which means as its altitude decreases the circumferential velocity would need to decrease. But gravity only pulls down, there's no force to accelerate it in that direction. So therefore it appears to curve off to the side.
Keep in mind that the object orbiting is already falling. Orbiting earth is literally "falling around the earth", compared to "falling down to earth" which we are more familiar with from throwing rocks and whatnot.
So to go "straight down" either it would need to orbit the sun (instead of the earth) and have its orbit intersect that of the earth, like the meteors we're worried about, or it would need to do a very strong deceleration burn.
Either you do that with atmospheric drag, or a huge amount of fuel. The weight of heat protection is much lower and more efficient than the fuel option.