the previous default of 0, 1 causes opt-1 bytecode to also be generated,
which is not used without passing `-O` to `python3` anyway, and doubles
the size of the resulting package

--- a/src/installer/__main__.py
+++ b/src/installer/__main__.py
@@ -29,7 +29,7 @@
         metavar="level",
         type=int,
         choices=[0, 1, 2],
-        help="generate bytecode for the specified optimization level(s) (default=0, 1)",
+        help="generate bytecode for the specified optimization level(s) (default=0)",
     )
     parser.add_argument(
         "--no-compile-bytecode",
@@ -68,7 +68,7 @@
     if args.no_compile_bytecode:
         bytecode_levels = []
     elif not bytecode_levels:
-        bytecode_levels = [0, 1]
+        bytecode_levels = [0]
 
     with WheelFile.open(args.wheel) as source:
         destination = SchemeDictionaryDestination(