Singles are often pressed to make even unsuitable relationships into long term ones when their friends get married, and the pressure can cause them to decide it is time to stop socializing with married couples. It does not signify a lack of caring on the part of either party, but being pushed into something can cause a rift. Rather than be angry at their happy friends, it is easier to wander away until life makes its own changes. In this way, being reunited with married friends can occur at a later date.
Even when a dating relationship is serious, it does not necessarily mean the two people will be able to form a long term or married relationship. They might have differences they keep out of the public eye that are too great for them to be together for long, and it could lead their friends into making incorrect assumptions. The pressure to propose marriage can become too great, but ending the relationship at the time might not work well for those involved. Leaving behind married friends can be difficult, but it will ease the strain that can cause a relationship to end prematurely.
Few people are interested in having friends and family give them advice on their most personal relationships, but married people believe they have the ability to help their single friends. Due to their superior position in retaining a relationship, they occasionally believe they know more than enough to be able to advise others. The result is a glut of relationship advice, and they fail to realize their single friends are unhappy to be given it.
There are many ways in life that friends can become separated, and most of them are not done by design. When the marriage of one person is involved, it is often best to wander away for a time until both people feel comfortable with their own lifestyles. Reuniting with married friends in the future should always be an option for a single person, and both parties are generally happy when it occurs.