My brother plays bass, and was the coolest person I knew growing up.  He's a great player, and had a Hofner that Mom and Dad helped me buy from him so he could get a Jazz Bass.  Of course, the first thing I learned to play was the melody to Macca's Yesterday..
 
John

bassists gets the girls...

some other bassist gets the girls...
 
There, fixed!  
 
(although things seem to have worked out quite well for me)
 
John

When I got over my I want to be a guitar god phase is when I discovered that I really wanted to be a bass player.  I also realized that good bass players are hard to find so I would have an easy time getting gigs if I practiced/learned as much as possible.
 
It also didn't hurt that I really started getting into both Rush and Primus at that time.  This was late 1991.
 
bassists gets the girls...
 
True story.

Two Words:
 
Klaus Flouride
 
Two More Words:
 
Dead Kennedys

Why bass guitar?
 
because bass ukelele just doesn't sustain enough!
 
 
Mike

Its the POWER.
Chuck

JAE and the coolest looking bass guitar ever (IMHO)...his Alembic Exploiter.

Aston family man Barett,1st inspiration
Robbie Sheakspear
and  
Stanley Clarke

Graham Central Station (The Jam)
The Who (My Generation)
Cameo (Shake Your Pants, Keep It Hot)
Isley Brothers (Livin in the Life, Climbin Up the Ladder)
Earth Wind & Fire (Feelins, Fantasy)
James Brown (Too Funky in Here, Get on the Good Foot)
Parliament (Tear the Roof Off the Sucker, Mothership Connection)
Funkadelic (One Nation Under a Groove, Cholly)
Brides of Funkenstein (Never Buy Texas from a Cowboy, Disco to Go)
Bootsy?s Rubber Band ? Any and all songs
Raydio (For Those Who Like to Groove, Hot Stuff)
Brick (Dazz Band, Dusic)
Tower Of Power (What is Hip)
 
The Brothers Johnson, Stanley Clarke, Lakeside, Mothers Finest, Brick, Average White Band, Charlie Mingus, Charles Fambrough, Anthony Jackson, Tyrone Brunson, Leroy Vinegar, Tyrone Brown, Ron Carter...

Do you know this one: a young guy comes to a bass-teacher and takes his first lesson, then they make an appointement for the second one but he never comes back. A year later they meet each other on the street and the teacher asks him why he did not come back to the lessons, the guy says: I?m sorry- too busy--too many gigs...!

I originally studied as an organist (theatre and classical) in my tween years.  When I rediscovered rock in my mid-teens in the 1970s, a Hammond was way too heavy to carry around, much less move.  Tried drums and that didn't click, then guitar - too damn many strings!  Traded the guitar back to the music store for a new 1972 maple neck P-bass and knew I'd found my instrument.  
 
A few months later, after I'd switched to a Rick 4001 (I worshiped C. Squire at the time) I saw a pic of Jack Casady playing Number One, the Mission Control bass.  At that moment I knew that someday I would have to own an Alembic. 26 years later my teenage dream came true!

I just picked up a bass that was laying around my school's band room one day about 4 years ago out of curiosity.
 
Still going...

Similar to other's comments,  they needed one and I was willing to put down my guitar.
 
...also its the closest thing to a pipe organ POWER,  
    ...and you get to touch and move the strings, as opposed to synth when you want to 'Dig in' you are a couple processes removed.  
   Piano is pretty close even though you don't (usually) put your fingers to the strings.

My old man used to play professionally so basses were the only instruments in the house,so at around 14 i just started picking them up!