There is no doubt that practice in any sport is essential to good performance.
Professional athletes spend almost very waking moment either training for or thinking about the sport they play and make their living with. At least successful ones do, and professional golfers are no different.
If you speak to a professional golfer or a golfer trying to make it to the big leagues on the PGA Tour and ask them how often they practice the answer will almost always be every day.
Practice does not always mean hitting the course to play the game either.
While many golfers will hit their home course several times a week when not out on tour, the vast majority of them spends much more time on the driving range or the practice green than they do actually playing a round.
Many top players will actually spend as much as 8 hours per day on the driving range depending on how they feel they are swinging the club at the time.
The hours they spend are used to work on the basic fundamentals of the game that can only be honed through many hours of training.
The game of golf requires that the player swing the club the exact same way pretty much every time they play which means that you need to train your muscles to perform a task the same way every time. The muscle memory that this requires takes many years to develop properly and that is why the top professionals spend so much time on the range and the practice green.
Even when out on the course practicing, the emphasis is on the ability to practice scenarios so that when you encounter one in a tournament the memory of that situation is seared in the brain and the mechanics become virtually second nature.
No golfer would succeed without putting in the time practicing and the best ones take that to the next level.