Cats groom themselves for a number of reasons: the saliva evaporation on the fur acts as a cooling mechanism; they are removing odor from food and bacteria that might make them detectable by a predator; much like brushing our own hair, the licking distributes the natural oils evenly through the fur, which guards against dampness and helps with thermoregulation; their saliva contains enzymes that act as a natural antibiotic and licking may help guard against infection; and they are fastidious clean-freaks!
Cats can also groom because they are comfortable in their environments but also as a displacement behavior to focus on the grooming, rather than the stressor.
Sometimes grooming can become excessive, and that's when it's time to pay a visit to your veterinarian. Excessive grooming can indicate skin problems, urinary blockage, and many other disorders.
I don't recommend guardians to bathe their cats - ever. If you cat stops grooming itself, there is generally an underlying medical issue and you should see your veterinarian right away. However, some of the long hair breeds do need help to keep mats under control, and aging cats could use a little help. Because removing a cat from its territory is so stressful on it, I highly recommend hiring a mobile groomer to come to your home. A good mobile groomer can also clip nails while there. In the Dallas/North Texas area, I recommend Loving Cat Care - check out their website here: https://lovingcatcare.biz