I can go on and on of bassists who were not frustrated guitar players
The term "frustrated guitarists" is actually not a literal term, but an affectionate one and one that describes a particular style of bass playing that went on to become very influential in the evolution of bass guitar playing and the position of the bass guitar, particularly in the various strands of rock music that developed from 1960 onwards. It also shines a light on the lowly position that the bass guitar had after its invention in 1952. It's quite an eye-opener to see what a stir of hatred and condescension it caused, particularly in jazz, when producers started picking up on it and realizing that it could now seriously compete with the volume of drums and electric guitar and made the double bass seem like a rubber band.
John Entwistle. Chris Squire. Players who defined the role in modern rock. Add John Paul Jones for all around musicianship, Sting for putting different genre bass figures into pure melody.
Chris Squire is an interesting bassist because he's one of the few bass players from the instrument's first 18 years {1952-70} that actually picked up the bass guitar without having started on another instrument. But, significantly, prior to picking up the bass when he was around 15, he'd spent many years as a trained chorister and before he took to the bass {and developed a love of the Beatles}, his sole musical interest was church music {interestingly, he grew up in Kingsbury where I live and he sang for years at St Andrew's Church ~ around the back, they have a nursery which both my kids went to} and he said that it was in those years that he learned most of what he knew about music.
Sting started off as a piano player before becoming obsessed with the guitar before he was even a teenager. He then became obsessed with the Beatles and up until 1967, learned every one of their songs on guitar. His mind was blown by Hendrix {he says seeing him live significantly altered his world-view}, and jazz took him to places yet unknown. When a friend first showed him a bass guitar, an instrument Sting described as "functional without being crude," he says he hadn't "really taken much interest in the instrument, regarding myself exclusively as a lead guitarist."
I won't even mention Wrecklng Crew 'member's
Ray Pohlman {one of the first session bassists as far back as the '50s} was a double bassist and guitarist, Carol Kaye started off on the guitar before turning to bass, Joe Osborne started on the guitar, Bill Pitman was primarily a guitarist, Max Bennett was a double bassist, Red Callender was a double bassist and tuba player, Chuck Rainey played viola, piano and trumpet before he got to the bass guitar, Lyle Ritz played double bass and ukulele, Chuck Berghofer played double bass as did Jimmy Bond; Bob West also played double bass and contributed to string sections - at one point or another, all of them "played" with the wrecking crew. It doesn't appear that any of them picked up the bass guitar as the first instrument they became proficient on. They were already instrumentalists, for the most part before it was even invented.
I can go on and on of bassists who were not frustrated guitar players
After 1970, I heartily agree with you. Prior to that most bassists came to the instrument through circumstances that they did not engineer, rather than through choice. For example, Wally Waller who played some neat bass with the Pretty Things in their psychedelic going into progressive phase {through "SF Sorrow" and "Parachute"} was a guitarist but he was a childhood friend of the group's singer Phil May and when the bass player John Stax left, May asked his mate to step in. Many of those initial early bassists would not have become bass guitarists had they been given the preference of the instrument they actually played. Even John Entwistle only turned to the bass because when he and Pete Townshend decided to play rock'n'roll instead of the trad jazz they'd been playing, Entwistle's trumpet and French horn couldn't be heard above the din. Entwistle actually said "I just wanted to be louder. I really got irritated when people could turn up their guitar amps and play louder than me. So I decided that I was going to play guitar....I did want to be a lead guitarist. The role of the lead guitarist was the most glamorous to me. I wanted to make solo spots in a group. And you don't go from being a frontman [which he had been as a trumpeter] to a back man." What got him to switch to bass was the size of his large hands which made it hard to twiddle about on the guitar and the fact that he liked Duane Eddy's low-note guitar playing and the fact that guitarists were ten-a-penny while bassists were almost as rare as hen's teeth in the late '50s.
I am primarily a guitarist but I have always held that really 'great' songs have great bass lines and most of those have been created by great bass players who chose bass over guitar in the end
After about 1970 I'd go along with that. But before then, bass guitarists largely made up how they played and much of that came from the instrumental mentality that they'd acquired before they turned to bass guitar. There really is scant evidence prior to the '70s of bassists actually deciding
not to go with guitar or keyboards in favour of being the bassist. If there ever was an instrumental evolution that is easily and uniquely traceable, it is that of the bass guitarist.