It may be that you have made friendships with people based on particular common interests. After a while, people's priorities change, they develop new interests, and then lose contact or interest in their old friends.
The few friends I have can be categorized into two groups. The first would be co-workers, and we basically only discuss work and work related things, and the other friends are members of a club I belong to. Since people's careers and interests are fluid, I suppose there must be some sort of fluidity in these relationships.
It is possible that outside of family members, the long term, close best-friendship, is not all that common in or out of the A.S. community. I believe there was a documentery titled something like "Bowling Alone" that delved into the issue. After all, we are more of a transient culture and most people don't even know their neighbors. If reality tv is really reality, I might not want to know my neighbors.
As for being fired without knowing why, I can only suggest that being entertaining and being able to network and go golfing and then have drinks with bosses and co-workers, etc... goes a long way in one's career. Not being part of the in-crowd at work can have serious repercussions with an employer.