Or perhaps they were previously married but are now widowed or divorced. Or perhaps they were never married because they could never find a suitable mate who was willing to marry them. God provides for all our needs, including our sexual needs. However, Scripture is basically silent on the subject of sex for the unmarried. So the following are my opinions, based on what I have learned so far in the Lord.
Some people are able to do completely without sex in any form.
Some people prefer to live without sex in any form. Solo Masturbation Is An Option God in His wisdom, placed our sexual organs in a location where we can reach them easily. And if we rub them for a while, we can usually get some kind of sexual release, sometimes a very satisfactory release. I find no Scriptural evidence whatsoever against solo masturbation, and I have looked hard for it. The Old Testament story about Onan is sometimes cited as Scriptural evidence against masturbation.