Based on your avatar I will assume you have an URB and let you live. But still don't tell my wife that one can live with only one EBG or all bets are off.
I own three. Two were GAS purchases but both have been justified. For months my Yamaha BB414 was out of action and during that time, I had enough around to still have a bass with a flatwound set and roundwound set. In an ideal World, I'd have one standard bass model that I really like and several identical basses as backups/different configurations but in reality, we all buy different basses because we like different things at different times. I bought my Yamaha BB414 as my first bass. It's a good, solid basic bass and it does me very well. It's had electrical gremlins that I've finally fixed. My Dean was a GAS purchase because the Yamaha was proving difficult to play (lack of practice, poor setup) and the Dean was very easy to play. It's only low-end but it's good enough as a backup and plays nicely - even though it could certainly do with a better pickup and hardware. My Rockbass Streamer was another GAS purchase. It's just a good all-rounder that plays well. It's my go-to. I bought it very cheaply on sale and it's proving to do everything. My BB414 will be its backup and the Dean will be my 'alternative' for different setups - e.g. flatwounds and alternative tunings. That's my justification for owning several instruments. Your mileage may vary.
I agree with the backup bass reasoning. I think it's also nice to have a cheap bass for travelling - so you can practice, but not worry if it gets lost, damaged, or stolen.
I am down to two basses, a Sadowsky JJ and a Sadowsky P/J. It helped me to learn that I prefer 4 strings. I love the idea of refining my skills instead of spending much time with my gear. My lead guitarist is the opposite, and I often wish he would spend all the time he uses for fiddling with his gear for simple, straight practice... Ah, and there is the fretless Yamaha BB404 that I keep purely for sentimental reasons.
It is just not good to sell or trade your first bass away. Most of us did and we regret it. I wish I still had mine.there really is a certain sound that is now stuck in your head of your first bass and it doesn't really leave. You might not believe me but you will miss it. Just put it in a case and put her away for awhile.
I don't. My first bass was an unmitigated piece of crap. I haven't missed it even once in 20 years of playing. My second one, sometimes I miss it, but it's for sentimental value more than anything.
I have a bass guitar, an electric upright and a double bass. My EUB is the NS Designs CR5M. It has magnetic PUs as well as the piezos. It can cop a very good slab tone for most all the stuff I do. I can usually use it to pull off anything "electric" unless it's a straight-up driving rock feel. I could do 85-90 percent of the stuff I am called for and never touch a EBG. Plus it looks wild. So, it actually sparks a little interest for the crowd!!
Fretted, fretless, active, passive, rounds, flats, four strings, five strings. Making money gigging means one either invests in gear or gives the bread to the IRS. It was a simple choice to buy more basses. John
I have had up to 10 basses at a time but I pretty much come back to a 4 fretted, a 4 fretless and a 5 of sort.
At one point not long ago I had ten basses. Now I'm down to five. Two Gibson, two Fender and a Carvin. Gibson Midtown Gibson SG Reissue Fender Jazz Fender Mustang Carvin AC40F Fretless Semi-Acoustic with tape wraps Two of my basses are short scale and two are long scale. One is Fretless. Different sounds for different styles.
The only reason one "needs" a second bass is as a backup. Beyond that, it's a matter of the variety and versatility.