Did you notice that since the invention of digital cameras (or at least DSLR cameras) you need to sharpen all (or almost all) of your images?
That’s because of low-pass filters on cameras (sometimes called anti-aliasing filters as well).
One of the main reasons why low-pass filters (or anti-aliasing filters) are used on digital cameras is to reduce so called moire patterning on images.
Moire patterning occurs when two linear grids are overlapped out of alignment with each other.
The same occurs when the grid of a digital camera sensor is exposed to a similar linear pattern, like for example brickwork on a building. Anti-aliasing filter is designed to blur the image slightly. Different manufacturers use different strengths of filter as well, so the stronger the filter the more blurred is the image. Using a low-pass filter to remove moire pattern impacts the image’ sharpness and that’s why digital images need sharpening.