It’s a major convenience when a tap is difficult to turn.. The major reason this occurs is due to a build up of limescale and debris to the inside mechanisms of the tap over many years. A lot of homes are located in hard water areas which puts more pressure on the plumbing mechanisms. Also the O-Ring after much use can become worn the surrounding parts of the tap to rub together and cause friction. The spindle of the tap can also which is the inner valve of the tap can become stuck.