Short-term solitude is often valued as a time when one may work, think or rest without being disturbed.
Long-term solitude is often seen as undesirable, causing Loneliness or reclusion, resulting from inability to establish relationships. However, for some people solitude is not depressing. Still others (e.g. monks) regard long-term solitude as a means of spiritual enlightenment.
A distinction can be made between physical and mental seclusion. People may seek physical seclusion to remove distractions and make it easier to concentrate, reflect, or meditate. However, it's not the end in itself and once a certain capacity to resist distractions is achieved, people become less sensitive to distractions and more capable of maintaining mindfulness and staying inwardly absorbed and concentrated. Some highly developed people (e.g. some Buddhist monks) can maintain very high concentration levels almost regardless of external circumstances. Such people, unless on a mission of helping others, don't seek any interaction with the external physical world. Their mindfulness is their world.