Except you may have just passed a cyclist without leaving enough time to turn because you barely registered their presence and are now going to cut them off. Or you stopped at an intersection and they approached on the right because that is where they are supposed to stay by law and you didn't check your blind spot before you started. The first situation can happen with cars where you pass a slow moving car just before an intersection and immediately slow down to turn right, merging back into the lane and cutting off the car. If you have driven any amount of time at all, I am sure you have seen that annoying scenario. The second situation doesn't typically happen with cars because of how right turn lanes are constructed but can (unlawfully) occur when someone (typically a tourist) was in the straight going lane but realized they wanted or needed to turn right.
Dedicated bicycle lanes are meant to make it clear that you are indeed crossing traffic when you turn right because bicycles as slow moving traffic are intended to stay in that area as an exceptional case.