Reply to what's the problem with beatmixing?

hey, i'm a digital dj .. and i know if I want to start playing in clubs the chances are very high I have to play on CDJ's so my biggest worry is beatmatching .. but what I dont fully understand is the problem of beatmatching.. beacuse isn't it true you can see the BPM of the tracks playing on the CDJ's so the only thing you have to do is get the BPM as close as possible and then just synce them? or am I missing something