If reverb is applied to a signal with a lot of lows and highs, this can have the effect of smearing the whole mix if you roll off the frequency extremes of the signal that is routed to reverb, the effect of pushing the part back in the mix is even greater. While reverb can provide a realistic simulation of an acoustic space, using a lot of it will smear the effected signal in the time dimension, and tend to push it back in the mix, making it sound more distant.
Reverb and delay aren't completely unrelated effects - reverb can be thought of as a network of many short delays.
