Clients need help with transfers because not all clients can get up on their own nor do we want them to in some cases. Without assistance on transfers, the client may be at an increased risk of falling when attempting to mobilize on their own, which can lead to additional ailments atop whatever conditions the client may already be living with or dealing with momentarily. For example, a patient taking a medication known to cause orthostatic hypotension requiring them to change positions slowly may need some help because if they become dizzy in this process and are alone in transferring from a bed to a nearly chair or to a wheelchair, the medical professionals must now provide aid for what the fall has caused and what the medication is indicated for.
Other reasons for assisted transferring of clients include helping the patients gradually increase their strength and re-train to perform such transfers independently (think learning to ride a bike; you usually start with training wheels, then with a hand on your shoulder while you learn to balance, then you learn how to launch and do it alone!) as well as to perform position changes as to not create bedsores and pressure ulcers.