[development] Postgres- For compatibility reasons we don't drop columns but rename them?

[Neil Drumm]

 From the documentation of hook_update_N():

Dropping a column:

MySQL: ALTER TABLE {$table} DROP $column
Postgres: ALTER TABLE {$table} RENAME $column TO $column_old // For 
compatibility reasons we don't drop columns but rename them

Why do we do this? What compatibility reasons?

-- 
Neil Drumm
http://delocalizedham.com/