It may look precarious, but learning into a corner on a motorbike actually offers more grip. As bikes only have two wheels, they don’t simply turn through corners in the way a four-wheeled vehicle does. Instead, they effectively carve through the turns, leaning from side to side and using the full outer radius of their tyres to maintain contact with the road.
When a biker leans into a corner at pace, a number of extra forces come into play to help the bike maintain grip. Firstly, camber thrust is created, which means a point on the outer surface of a leaned, rotating tyre that would normally follow an elliptical path when in contact with the ground is forced to follow a straighter path. Meanwhile, as the bike tracks round a bend, the cornering causes a centrifugal force to press the tyres into the road, ensuring grip is maintained.
The harder a tyre is pressed into the ground, the more grip the tyre enjoys, and thanks to centrifugal force and camber thrust acting against the tyres here, more weight is essentially put on the vehicle when leaning over. A bike therefore technically has more grip through a corner than it does when vertical in a straight line, despite the same amount of tyre surface area being in contact with the road.