There are several methods for keeping dreadlocks neat. As they grow, little wisps of short hair will appear around them. If you leave them, eventually the dreadlocks will settle down and form their own natural way of sitting - afro-caribbean hair usually does this, but caucasians might like to wax their hair, sew the wispy bits in, or wrap thread or wool round their dreadlocks, sealing the short hair in.
As they go they can be "ripped". Two (or more) dreadlocks fuse at the top as the hair grows and mats together. They need to be pulled apart for the dreadlocks to continue growing separately (although this is down to the individual). This hurts!
There are many reasons for wearing dreadlocks. For some it is a religious issue (such as the Rastafarians), for others a fashionable thing, for a few they just happen. They are considered a badge of an "alternative lifestyle" in Europe and America because they are often perceived as messy and dirty.