Typical causes are mud filtrate and solids, a crushed perforation tunnel, scale, fines, wax, or a completion fluid that swells clay. It appears as positive skin and as a productivity index below what the permeability and the net thickness would suggest.
The damaged zone is small, which is why an acid job or a short fracture can restore the rate: the extra pressure drop is concentrated where the flow area is smallest. Damage is not a low reservoir permeability. A tight reservoir was tight before the well was drilled. Damage is what the well did to the rock.