We recommend cleaning gutters 3 times  per year, with one of these possibly being a check up.  

Having debris in your gutters can cause them to backup, rot, and fall off. Gutter failures can also cause your roof to leak.   

In this example this owner needs gutters cleaned, a fascia return re-flashed, and a gutter re-pitched and reattached.  These aren’t necessarily all directly caused from backed up gutters, but they can be, and they can cause all sorts of other issues.