In most languages, variables can contain different kinds of values. For example, in Python a variable can be a number that you can do arithmetics on (
a-1), an array or string you can split (
a[3:]), or a custom, nested object (
In bash, you can't do any of this directly. If I understood you right, you asked why this is.
There are two reasons why you can't really do the same in bash.
One: environment variables are (conventionally) simple key=value strings, and the original sh was a pretty thin wrapper on top of the Unix process model. Bash works the same, for technical and compatibility reasons. Since all variables are (based on) strings, you can't really have rich, nested types.
This also means that you can't set a variable in a subshell/subscript you call. The variable won't be set in the parent script, because that's not how environment variables work.
Two: Original sh didn't separate code and data, since this makes it easier to work with interactively. Sh treated all non-special characters as literal. I.e.
find / -name foo was considered four literal strings: a command and three arguments.
Bash can't just decide that
find / -name now means "the value of the variable find divided by the negated value of variable name", since that would mean everyone's find commands would start breaking. This is why you can't have the simple dereferencing syntax other languages do.
$name-1 can't be used to substract, because it could just as easily be intended as part of
$name-1-12-2012.tar.gz, a filename with a timestamp.