Why Linux always show size in bytes no matter how?

We have an old Linux server, some OS version information, as follows:

$ uname -a
Linux dm.inside.com 2.4.18-17.7.xsmp #1 SMP Tue Oct 8 12:37:04 EDT 2002 i686 unknown
$ cat /etc/redhat-release
Red Hat Linux release 7.3 (Valhalla)

No matter how I issue 'ls', file size is always shown in bytes,as follows:

$ ls -l catalina.out
-rw-rw-r--    1 qbase    qbase    13136665 Aug  1 13:00 catalina.out
ls -lk catalina.out
-rw-rw-r--    1 qbase    qbase    13136706 Aug  1 13:01 catalina.out
$ ls -l --block-size=1024 catalina.out
-rw-rw-r--    1 qbase    qbase    13136706 Aug  1 13:01 catalina.out

'alias' command shows that 'ls' command is not aliased. So what could be wrong?

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