What does a tonearm contribute to the sound of a turntable?

Without one the sound is very attenuated.

Read most of this and have a question.  Back in the "old days" there were controversies regarding detachable heads and fixed heads.  The Shure (SME) 3009 had detachable heads and others had fixed heads.

I remember many articles that preferred the fixed heads for many reasons.  (The detachable ones were much easier when changing cartridges, as I remember!)  Has this changed with today's arms?

Back then, Linn Sondek had the better belt-drive tables and Technics came out with direct drive and everyone was crazy over that technology for a while.

Since I still have both types of tables from back then, I was wondering what today's world finds most accurate in drive types for tables, and which arms are considered to be the most accurate (fixed vs detachable)?

Cheers!

Maybe the proper question is what does a turntable contribute to the sound of a tone arm?

In a perfect world a tone arm contributes nothing to the sound. It just allows the cartridge to track the record and convert mechanical squiggles into electrical impulses. Practically it adds distortions. The better ones add less than the mediocre ones. 

I still don't understand the fascination of using vinyl.  Unless people love the sound of noise caused by tracking on a groove.  Noting like the sound of noise when hearing music.  Streaming music is now the future.  Quit buying expensive records and turn tables and realize your turntable is headed for the museum.  You don't see phonographs anymore.  Who wants to get off the sofa, take a vinyl record off the turntable, find a new one to listen to it, clean the record and get another record started when you can sit on your seat and select a huge selection of music by using your cell phone to do so.  The money you spend on a turntable and records could be spent on upgrading your speakers and amplifiers.