Anything that impedes your ability to steer the car in the desired direction is a problem. These days, the steering wheel is unlikely to fall off in your hands. Nor will the steering column sheer off, unless you’ve dodged the MoT man for several decades. When it happened to me, I felt the wheel lighten and braked before it did anything more dramatic.
Power steering is the principal culprit for what we commonly call steering ‘failure’ in a road car. Manufacturers these days are designing their vehicles’ suspension a bit like the extended front forks on a Harley Davidson. The benefits include greater fuel efficiency and cornering stability, at the expense of making the steering so heavy that it’s practically impossible to turn the wheel without power-steering assistance.
If your power steering fails in a corner, then it will be time to test those muscles and drag the wheel to where you want it. Power steering tends to fail in fits and starts, rather than all at once, so as soon as you notice the first heavy hints you should get it fixed.