It comes down to equality. Values have "extensional equality" which means that values A and B are equal exactly and only when they look the same and can be used in the same way. On the other hand, most people are used to "referential equality" which is more strict. It lets me distinguish "your copy" of A from "my copy" of A via their names.

Without referential equality things like mutation fail to have any sense, but programs are in general simpler.