Clubs are eager to attract societies to their course as the fees charged can be quite substantial. The best thing about societies is that they are relatively informal and particularly suit the occasional golfer from a cost perspective. It is not necessary to maintain a handicap through affiliated club membership yet one still gets the opportunity to play in competitions and enjoy social events. Of course, club and society membership are not mutually exclusive. If you are an occasional golfer and can't be bothered with joining a club or society then you can still enjoy golf.
Many clubs are happy to accept visitors without a handicap certificate.
There are also plenty of hotels, country clubs and privately run courses which are not run in the traditional manner and happy to accept visitors. More and more clubs are adopting the 'pay and play' principle where you just turn up, pay green fees and play. It is also usually possible to play the few remaining clubs if accompanied by a member.