Why are transits of Venus so rare?

Question

Earth and Venus move in opposing directions, so transits shouldn't be that rare. Is this because Earth and Venus have different tilts?

Answer 1

Earth and Venus both have prograde orbits, although Venus does have retrograde rotation. The reason for the rarity of the transits is indeed due to orbital tilts. Earth's and Venus' orbits form a 3.4 degree angle to each other. The transits only occur when the two planets have a conjunction on the line where their orbital planes cross. During other conjunctions, Venus would appear to pass above or below the Sun.

Answer 2

Simpler version of the above answer. Yes, you are right.

The orbits are not flat. Their tilt almost always means that Venus passes above or below the Sun.

Transits of Mercury are more frequent because Mercury is much closer to the Sun. Even though its orbit is tilted to, the tilt isn't enough to almost always take it above or below, like Venus.