yum remove leaves empty directories

Hi,
here is my spec file which i generate using maven :

%define groupname %{name}
%define username %{name}
%define __jar_repack 0
Name: flock-snippets
Version: 1.0.0
Release: 1
Summary: snippet
License: (c) null
Group: Application/Collectors
autoprov: yes
autoreq: yes
BuildArch: noarch
BuildRoot: /Users/robinsuri/Checkout/flock-snippets/target/rpm/flock-snippets/buildroot

%description

%install

if [ -d $RPM_BUILD_ROOT ];
then
  mv /Users/robinsuri/Checkout/flock-snippets/target/rpm/flock-snippets/tmp-buildroot/* $RPM_BUILD_ROOT
else
  mv /Users/robinsuri/Checkout/flock-snippets/target/rpm/flock-snippets/tmp-buildroot $RPM_BUILD_ROOT
fi
chmod -R +w $RPM_BUILD_ROOT

%files

%attr(-,flock-snippets,flock-snippets)  "/opt/flock-snippets/snippet.jar"
%attr(-,flock-snippets,flock-snippets)  "/opt/flock-snippets/flock-snippets"
%attr(-,root,root)  "/etc/init.d/flock-snippets"

%pre
#!/bin/bash
getent group %{groupname} >/dev/null || groupadd -r %{groupname}
getent passwd %{username} >/dev/null || useradd -r -g %{groupname} -s /sbin/nologin %{username}
install -d /var/log/%{name} -o %{username} -g %{groupname} -m 750

%post
#!/bin/bash
PATH="$PATH:/bin"

echo "Checking environment for prerequisites"
chown -R %{name}:%{name} /opt/flock-snippets
chmod ug+x /opt/flock-snippets/flock-snippets
chown -R %{name}:%{name} /var/log/%{name}
chmod g+s /var/log/%{name}
echo "Environment setup done"

cd /opt/flock-snippets
/sbin/chkconfig --add snippet
/sbin/chkconfig snippet on
chmod +x /etc/init.d/snippet
service snippet start

%preun
#!/bin/bash
if [ "$1" -eq "0" ] ; then
    /sbin/service snippet stop >/dev/null 2>&1
    /sbin/chkconfig --del snippet
    cd /var/log
    rm -rf flock-snippets
fi

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When i do yum install
It creates the folder /opt/flock-snippets
and two files under it flock-snippets and snippet.jar

But when i do yum remove flock-snippets.rpm
It does delete those two files under flock-snippets
But leaves the flock-snippets folder as it is empty.

Is this a normal behavior or i am doing something wrong.

Thanks