Why not support wildcards (foo/*) when reading files from a folder in hdfs?

I just encountered such a problem in learning Hadoop get started

-sharp 
bin/hdfs dfs -ls
drwxr-xr-x   - zhugw supergroup          0 2018-11-17 17:11 output
drwxr-xr-x   - zhugw supergroup          0 2018-11-17 18:02 pv_users_count

-sharp 
bin/hdfs dfs -ls output
Found 2 items
-rw-r--r--   1 zhugw supergroup          0 2018-11-17 17:11 output/_SUCCESS
-rw-r--r--   1 zhugw supergroup        220 2018-11-17 17:11 output/part-r-00000

-sharp output
bin/hdfs dfs -cat output/*
6    dfs.audit.logger
4    dfs.class

-sharp 
 bin/hdfs dfs -ls pv_users_count
Found 2 items
-rw-r--r--   1 zhugw supergroup          0 2018-11-17 18:02 pv_users_count/_SUCCESS
-rw-r--r--   1 zhugw supergroup         21 2018-11-17 18:02 pv_users_count/part-r-00000

-sharp pv_users_count
bin/hdfs dfs -cat  pv_users_count/*
zsh: no matches found: pv_users_count/*
-sharp 
bin/hdfs dfs -cat  pv_users_count/part-r-00000
1,25    1
1,32    1