One of the most rediculous and hypocritical statements that one can ever make is telling someone not to change. For, wether they like it or not, people are always changing. Alot of people dont notice it because they are changing with their friends. look at it like a river. From shore, it looks like the river is moving, but for those chaging (on the river) it is the shore that is moving. Thus when everybody is in the same boat (nice analogy I get 5 extra points) they don't look like they are moving to each other.
So why then would someone ask another to not change? because they like where they are now. They enjoy the situatiuons they put themselves in and the consequences there of, good or bad. These people can't accept that all people change, except the dead. So asking someone to not change is asking them to drown. You literally push them of of the boat and onto the shore. Is that really what you want.
If by some miraculous chance a perosn is able to stay the same, and you continued on in your life for a few years and came back, things would be different because you changed. Just imaginge what will hapen when two people change at a time, major change action goin on there.

Unfortuntatly, nature has a way of making life difficult. So I think there are things that don't change too much or at least not very quickly. One of those things is a person's personality. The kinds of traits they have. Things like how much a person cares about certain things, or whether they like or dislike doing stuff. Food is a good example. Not very often do people all of the sudden like the foods they loathed in the past. It simply just does not work. So, you can't really tell people to change either. Isn't that a shame. Well, even if you did, the person you told would have to have a serious passion for changing.
Plus, to change, it takes major life events or events that push your limits and improve you. Kinda like going to a ropes course or on a wilderness trip. Those things test your strengths, weaknesses, and end up changing you as a result of the exerience. In other words, people don't change on a whim. The point is that if you don't like the way they are, there isn't much you can do about it. Either leave or get used to it.

... wow that was dark