Why might a satirist offer ironic, rather than direct, criticisms of institutions like church and state?

To me, there are at least three reasons that I can think
of:

1. It makes for a more interesting piece of
   writing.  If you were just to write an essay about what you thought was wrong with
   government and religion in England, people would not be too likely to buy it.  Make it
   into a fun book like Gulliver's Travels and more people will
   buy.


2. It makes people think.  If you read the book and you
   have to think about what it is saying (you have to figure it out) you're more likely to
   really remember and take it to hear.


3. It might be less
   likely to make people angry.  It doesn't directly attack things and so people who like
   the institutions might not get as mad.