There are many kinds of physical disabilities. Some of them can be quite extreme. Physical disabilities can manifest in such a broad range of ways for many reasons. People can be born with physical disabilities or acquire them later in life due to an accident or old age.
Common mobility problems include tremors, shakes, becoming easily exhausted, or experiencing difficulty in movement. Many people with physical disabilities cannot use a mouse at all and therefore have great difficulty if websites are not keyboard accessible. In fact, ensuring your website is keyboard accessible is probably one of the greatest things you can do to help users with physical disabilities.