There are times when intensity is needed. In BDSM, there is a concept
of good pain... something that hurts but feels good anyway.
From the Deviant Dictionary: Pain is, in broad terms, the body's warning that something is wrong, but our pain responses are very complex and it is very easy to produce the effect of pain without doing any real harm; the pain threshold, at which a stimulus crosses the boundary between intense sensation and pain, is also a grey area in terms of our perception, and can vary according to context.
SM is associated in most people's minds with potentially painful activities, sometimes referred to as paingames (for example various kinds of flagellation or torture, and it is true that some people directly enjoy, or at least get some other kind of satisfaction out of, intense physical sensation. Most of this, however, is on rather than decidedly over the pain threshold, and some of the satisfaction may be attributable to the release of body chemicals such as endorphins. And there are other aspects of SM: most players' interests are a mixture of the physical aspects and the psychological dynamics of domination and submission, and some play with hardly any physical pain at all. Those for whom the interest in pain predominates are sometimes referred to as sadists and masochists rather than dominants and submissives.