If you didn't have friction everything would be awfully slippery. It'd be hard to hold on to the grips, the tires would spin on the tire, and on the road. Braking wouldn't work. Bolts would come undone etc etc.
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Without friction, the bike would slide all over the road. Holding on the grips would be very difficult. Keeping feet on platform pedals would be difficult.
These places, and some more, friction is useful.
W/o friction, the tires would slide on the rims and on the road. Holding on to the bars would be difficult.
OTOH the Wheels would spin forever, there'd be no air drag and the saddle would never chafe.
Without friction the tires would slip all over the road, grips wouldn't stay on the bar and the rider wouldn't be able to stay in the saddle.
W/o friction, the tires would slip on the ground, and against the rims. Handles would be really hard to hold on to and it'd be real easy to slip off the pedals.
Friction lets you steer, accelerate and brake without sliding all over the road. Friction lets you hold on th the grips.
Without friction, the tires would slide on the rim, and on the ground. Nuts and bolts would shake loose. Your hands would slip off the bar and your feet off the pedals.