Why are famous duos never known by a reversed combination of names (e.g. Garfunkel & Simon or Oates & Hall)?

We ar so used to hearing them the way they are, the reverse sounds funny. Cher and Sonny.

Because that’s how they bill and promote themselves.

Dear Starr Estrella, I have no idea. 

 

  Trivia item: in the English language, a little over half of well known pairs of people, places, and things are in reverse of alphabetical order. A few of the hundreds of examples:

Romeo and Juliet 
Lewis and Clark
Laurel and Hardy
Stanley and Ollie
Burns and Allen
Rogers and Hammerstein 
Simon and Garfunkel 
Starsky and Hutch
Salt -n- Peppa
Tom and Jerry
Mario and Luigi
William and Mary 
Rod and reel 
Trinidad and Tobago
Salt and pepper
Macaroni and cheese
Milk and cookies
Peas and carrots
Fish and chips
Pots and pans
Soup and sandwich 
Spic and Span
Track and field 
Sword and shield
Skull and crossbones 
Pen and ink
Dollars and cents
Song and dance
Skin and bones
~

All reversed and only four brace of people:

Low & Lerner
Swann & Flanders.
Wise & Morecambe
Sullivan & Gilbert
cream & strawberries
dies & taps.....*   
eggs & bacon
then & now
Sensibility And Sense
beck-and-call
answer & question
thread & needle

,...*Basic metalworking tools, complementary, and traditionally named "taps & dies".