That's because each individual grows in a new direction. All of the sudden you don't click anymore. That keeps it fresh. It hurts some people's feelings, but it also nurtures growth in musicians. It's often a good sign.
Some people fear change, but in jazz, change is usually for the best.
At one time, I was going to be a classical percussionist and try for the orchestra, but the drum set always called. And I'd talked to a retired timpanist who had played some of the same Beethoven symphonies 200 or more times, and that's hard to do. All the great jazz bands have great drummers. You may not notice the drummer so much in a rock band-the great jazz groups had killer drummers. But it's more than that.