The self-grooming process removes some - but by no means all - of the shed undercoat, and what the cat removes by licking is probably going to be brought back up later as furballs on your carpet.
The remaining dead undercoat remains trapped, to be shed onto the furniture later, or - more concerning for your furbaby's well-being - available to form knots and eventually grow into matts. Matting causes the cat pain, as every movement yanks at their fur by the roots, which in turn can lead to behavioural problems (quite understandably; I would be cranky if my hair was being yanked every time I moved too!). In the long term, skin infections can form beneath matts, which can be very serious for your kitty's health and require veterinary treatment.
Cats also cover themselves in layers of dried saliva when they lick, which can lead to problematic odours and aggravate cat allergies - since it is generally a protein in cat saliva and their dry skin flakes (dander) that people are allergic to, not the fur!
So, yes you should probably still get your cat professionally groomed.
Professional grooming removes existing knots/matts and
the shed, trapped undercoat, meaning a far reduced risk of new knots forming in the next 4-12 weeks (at least). The specially-designed products used by a good cat groomer improve coat and skin health, reducing dandruff after regular use, as well as keeping that fur glossy! A professional Full Dry Groom can include the use of dry/foam shampoo, which can help reduce odours and allergens deposited in the cat's coat when they lick themselves. A Full Wet Groom and blow dry completely removes allergens, meaning that if allergies are your primary concern you ought to ask your specialist cat groomer for a wet groom (using water and shampoo) if they offer that service and your cat's temperament will allow it.
Plus, you should notice reduced shedding on the furniture and fewer furballs for a while after the appointment too, due to the far reduced trapped, shed fur in their coat left for them to shed or swallow; its a win-win!
It could be that you have never noticed any knots or matts in your cats fur, and it could be they are lucky enough to have fur they can easily self-manage, with a little bit of combing or brushing from their purrent at home. But it could also be that they are too young to have developed problems with their coat. As cats age they become less mobile and less able to reach every area, leading to matts developing, normally in the "problem areas" of armpits, hips, bum and maybe shoulders.
Older cats (and indoor cats, and most especially older, indoor cats!) are also particularly prone to thickened and ingrowing claws, which is as painful as it sounds and often goes unnoticed for longer than we would like, because cats are masters of hiding their pain (and often don't like their paws being touched or examined)!
As a groomer I always recommend bringing cats in to your local cat grooming specialist for their first groom at as a young age, and keeping them on a regular maintenance schedule throughout their lives. This applies especially if they are long haired cats, semi long haired cats, or short haired cats with a very thick, very oily coat. These types are very prone to developing problems with matting sooner or later and the better acclimatised to grooming they are, the better for everyone. This "prevention rather than cure" approach means problems like matting and ingrowing claws never occur in the first place, which surely is preferable to any purrent.
However, I should add that Feline Good are totally here for you if your adult or senior cat has coat or claw problems that need treatment, so please don't hesitate to get in touch to discuss your grooming concerns.