A kerb is expensive to install, so someone put it there for a reason...
In low-speed environments, kerbs are effective at channelling traffic and can provide some re-directive capacity for low-speed impacts.
On higher speed roads, the main function of curbs is to provide drainage and they are mostly used in areas of a bridge approach or other locations with erosion risk.
In both these cases a hidden kerb is not performing it's function. This material will be preventing water run off, blocking drains and will act more like a ramp than a re-directive for traffic! So having a clear Kerb is important.
It also looks much more attractive to have a crisp clean kerb!
A weedbrush is the perfect tool for keeping a kerb clear, but some weedbrushes are designed for heavier work than others. The UBS is designed to deal with heavy soil all day long, while being easy on the operator.
For more information on the UBS and weedbrush please check out this link;