PVCu fascias, soffits and gutters can become grimy from pollution, mould and rainwater running down from the roof containing minerals that adhere to the surface, becoming calcified, and can only be removed with chemicals.
Your roof is possibly the single most expensive item that may need maintenance or repair, so it makes sense to keep it in tip top condition. Over the years the surface of roof tiles is eroded by the weather and acid rain causing them to become porous.
Keeping your gutters clear of debris is an important part of maintenance to the outside of your property. So much so that most house and home insurance companies insist on it as part of the cover. Leaves, twigs and moss can build up along the gutter, slowing down the run off of water and increasing the weight being supported by brackets and fascias.