脚本问题疑问

platform="$1"
all=",386,amd64,armv5,armv6,armv7,arm64,mips,mipsle,mips64,mips64le,ppc64,ppc64le,s390x,"
result=$(echo $all | grep ",${platform},")
if [[ "$result" != "" ]]
then
  echo "Your router platform: $platform"
else
  echo "Unknown platform: $platform"
  exit
fi

这里为什么不写成uname -m
platform=`uname -a`
让系统自动来判断架构？