it can be harmful when rubbed against skin
bad friction is when 2 things rub together .
Friction isn't always bad, but when engineers try to avoid or reduce friction, it is because of the energy lost due to friction.
Friction is good because it provides traction. Friction is necessary for people to stand, or for vehicles to accelerate or break. Friction can also be used to convert kinetic energy to heat or electrical energy. Friction can be bad because kinetic energy is can be lost to friction.
botch
No friction is not always bad. In fact consider an example of running on wet floor. If there is too little friction it might cause you to slip and slide.
it wears things away
It can be bad when a gymnast is on bars because too much friction between the bars and the hands can cause calluses/skin to rip off and leave the skin raw and/or bleeding. This can make practicing on bars very painful for a gymnast.
if it is an advantage then it can't be bad
Pushing a heavy rock
Friction can be either good or bad depending on where it is. Friction between parts that are meant to stay put is a good thing, friction between parts that are supposed to move is a bad thing. Tires for instance are meant to roll along the road, not slide. Here, friction is good. But then you cone to the hubs. In here, the wheel has to move around the axle. Here, friction is bad. Here, friction will turn effort that would otherwise have gone into moving the bike forward into heat, which is no use to the rider at all.
Grazing your knees and hands when falling over and sliding on a hard surface is caused by friction with the ground. A spacecraft returning to earth will heat up to red hot due to friction with the atmosphere. These are just two bad effects of friction. But, there are good effects, too. Friction from your vehicle or bicycle brakes will bring you to a stop! Friction from your tyres and the road surface will prevent you from skidding.
Having a lot of friction can be bad when you want smooth motion between two surfaces, as it can cause heat, wear, and energy loss. In some cases, high friction can also lead to difficulties in moving objects or machinery.