I recently spent half a day removing block paving moss from my driveway. The paving, laid in 1993, has been cleaned more than once but moss soon grows under damp conditions.
Because the blocks have a chamfered edge there is a V shaped recess at the junction between blocks. This is a space where moss can grow, and boy does it grow. Within this gap moss doesn’t get worn away by traffic (cars or feet).
Given a good wet period the moss swells in size until it sticks up above the blocks. Under those conditions it can become very slippery under foot giving me good reason to remove it.
You might ask why I’m only discussing moss and not regular weeds. That’s because I use weed killer during the spring and summer so I’m just left with moss in the autumn and winter. This is because regular weed killers are not effective against moss. Moss killer is effective at turning it black but at some point the dead moss needs removing.