Formal music education gives you tools to know/understand what you need to know, and how to get there. I played for 20years, relatively successfully, before heading to Berklee where I DID graduate with a BS in Perf on EB. There is sooooo much good to be said about the experience and what I took away from it. I am far better off for it and would do it again. History of Western music doesnt make you "gig" better but it does add value on your perspective of various performance opportunities you may run into. Ear training, harmonic analysis, counterpoint, 4 part writing, all invaluable music school expriences in getting you to think about the mechanics of music, and despite some posters on this site's very erudite and articulate attempts to discredit those experiences in relation to playing the bass it DOES make you a better player, and more importantly, musician, indirectly. The older I get and the more I play the more Ive come to understand that its all about being a whole/complete musician, not about your wicked slap chops or how fast you can play Donna Lee, though those things are cool albeit mostly to other bass players! Also, while at a school like Berklee you do get 2 private lessons per week and you have WAY more time to practice than if you are not going to Berklee, so in terms of direct impact on your playing, it is almost no contest.
The old "those who graduated are not really good..." is definitely an urban legend. Since I have seen mediocre players get picked up by major artists prior to graduation, and astounding players go the full 4 years. Just off the top of my head I could name a few that were at Berklee with me. Those who get picked up are either lucky or they work really hard at seeking it out. There are many avenues a player can take. Carving out a living as a hired gun to back up major artists is somewhat different from making a living as jazz musician, or a session ace, or heading up your own band, or being a big fish in a small pond if you choose to, or cant, be on the road.