Lisp programmers already tend to use the indentation the way adopted by Python. Add more rules for indentation and newlining, and voila: all or almost all parentheses become superfluous.

(But you need to really like white space!)

Brackets make macros easy, because they make the abstract syntax tree blatant. Make it less blatant, and macros will become much more difficult to write. Given the options of i) macros are easy to write, and ii) Python-style indentation rules enforced by the interpreter/compiler, I'll take (i).