Why does Gulliver's Travels have "teasers" at the beginning of each chapter?

I've seen summaries like these used in other novels of the time period. I believe they exist simply for the convenience of the reader, much like tables of contents and back cover summaries, and aren't intended to be interpreted as Gulliver's voice.

Other books of the time followed the same format: including Tristram Shandy (1759) I believe even "Pamela" (1940) did this but don't hold me to that since I haven't read that for 40 years.

In those days longer works were often serialized and this may represent an attempt to make the work more friendly to serial printings...Swift published in fear of prosecution, so it was not unreasonable to expect that the work would end up being circulated by alternate printing methods.

A lot of authors in that times used this trick in their works (as Jules Verne, for example, or ).

In that times book pages can easily shuffle (and not all books contained page numbers), and reader (and editor), using this summary, can restore page order.

Also you should note that this books are considered as children-oriented, and this summaries can easily make some attention, and add some magic atmosphere to the story (as in A.A. Milne stories).