The Stones didn't demand it, their former manager Allen Klein did. Ironically, the last person that got the money was producer Andrew Oldham who was pretty much solely responsible for writing and producing the string arrangement that was actually sampled (and I doubt the session musicians that actually played the instruments saw a penny)

tbf the Verve had the 18th best-selling UK album of all time and two other top ten hits off the back of Bittersweet Symphony's airplay, so I think they still ended up in credit

Are session musicians typically given royalties? I assumed they are just hired to to a job and are given a payment for time in studio.

It wasn't a Stones song that was sampled — Andrew Oldham Orchestra had done a cover of it in 1965 [1]. As I understand it the Stones had been ok with that, and then subsequently, he was ok with The Verve sampling some of it...until the Stones' former manager took exception [2].

[1] https://www.youtube.com/watch?v=MKC5cdGBY04

[2] https://en.wikipedia.org/wiki/Bitter_Sweet_Symphony#Song_cre...

Session musicians don't usually get writing credits. Nor do session arrangers.

Occasionally the session players get a credit if they've spent time with the artist co-writing the song.

The difference between making a session contribution and co-writing the song is ambiguous and contested.

As a guide, adding a single instrument line doesn't count as co-writing - not even if the line is so distinctive it effectively makes the song. (This is grossly unfair, but it's how it is.)

A string arrangement doesn't count as co-writing either. Not even if it adds a catchy tune.

Arguing with the performer/producer about chord sequences, lyrics, the main vocal melody, and song structure does count as co-writing. But session musicians who do this are on thin ice if they try it without tacit permission.

The irony being that "The Last Time" by the Stones, was a rip off of the Staple sisters