it's not the same thing.
VAR must take priority over LET, because you cant operate between undefined variables in an explicit environment.
this probably doesn't happen anymore in modern languages, but in old systems that was the case: VAR was the definition, LET was an instruction.
nowadays, it's assumed that any line involving variables with no instruction is an operation.
that actually ties to the fundamental structure of all languages: data structures, instructions, control structures, procedures and objects.
instructions are easy to spot: it's anything usually colored blue in the form of a block, they start with a key word, and end in ;, }, or "end"
control structures are larger blocks and contain several instructions (fixed loops, open loops, single conditionals, case conditionals, etc)
procedures are collections of control structures and instructions, usually returning a value, or returning to a previous line after going out of a main procedure.
objects are larger structures containing all of them, usually saved to files.
"but, what are instructions that *don't* have an instruction, such as straight operations between variables?" you might say.
.....that's exactly what LET was used for.... it used to be an instruction.