In this article Ron Drummond writes:
Joseph Haydn didn't have to write string quartets. His duties as Kapellmeister to the princely Eszterhazy family kept him extremely busy. Twice-weekly concerts required a steady stream of symphonies from his pen. Rehearsing his musicians, managing the purchase, maintenance, and repair of the orchestra's instruments, supervising a small army of music copyists, and smoothing over quarrels between players or disputes with the managers of the royal household was more than enough to fill his days.
Yet Haydn still took the time to write string quartets, even though, in the course of over forty years with the Eszterhazys, he never once received a royal directive to do so.
It would appear that Haydn began writing quartets for the pleasure of it; even though his "royal directives" would have had him writing symphonies (which he did, and a lot of them). It's not that Haydn didn't get pleasure from writing other things, but it appears as though the string quartet was something very special to him, and it shows in the exquisite simplicity of these works. They are joyful pieces for the most part, and one can imagine the festive occasions for which they were first played.
Plus, as Drummond writes:
Haydn sought to improve his art by the thorough exploration of musical forms and textures, and by bold experimentation. And what he came to discover was that the string quartet provided the most concentrated forum in which to do this.Keep this in mind as you listen to some more of Haydn's quartets:
String Quartet No. 66 in G major, Opus 77 ("Lobkowitz Quartets), No. 1, HOB III:81 - I: Allegro .moderato - Composed - 1799 - Played here by the Jerusalem Quartet.
String Quartet No. 66 in G major, Opus 77 ("Lobkowitz Quartets), No. 1, HOB III:81 - II: Adagio.
String Quartet No. 66 in G major, Opus 77 ("Lobkowitz Quartets), No. 1, HOB III:81 - III: Menuetto.
String Quartet No. 66 in G major, Opus 77 ("Lobkowitz Quartets), No. 1, HOB III:81 - IV: Finale: Presto.
And for more information on the Haydn String Quartets, I give you the following links:
The String Quartets of Haydn
The String Quartets of Joseph Haydn
Haydn's Joke: Humour in his String Quartets, Opus 20 and 33
Joseph Haydn: String Quartets, Opus 76
Haydn: The Complete String Quartets (Recording)
And you can take this Quiz when you're done. Just for fun.