How can you expect some-one to know how to please you sexually if you don't know how to do it yourself? These guides are a great way to discover and fine-tune what works for you - and then to pass that information on to your partner.
Most people masturbate whether they are single or in a relationship. Those in a relationship might practice on their own to offset differing levels of sex-drive, misaligned schedules - or just because they can!