Coming from the DB world, and having switched to a doubler only a few years ago, I have a bit of a different perspective. The big basses have a very limited range of tone. You can have the acoustic timbre or the other one, and those are it.
The reason that *I* like bass guitar is all the different timbres and volumes and effects and stuff. A giant tube amp and a 810 blow my pants legs around - there is NO part of that that doesn't kick a$$, regardless of your genre preferences. Bootsy wouldn't be Bootsy without a rack full of effects. Metal as a genre would be dead-as-fried-chicken if it all had to be played on classical guitars. The range of tone and volume required for different genres ranges widely and I love to be able to change it up and use things like a crunchy lead tone or a wokka-wokka phaser or change strings to a set that rings like a piano or have a pedal tone that sustains for long periods or a giant earthshaking dub line.
Also my strings are like $30 for flats that last forever. I'm saving up for DB gut strings that cost $400 (also take a year to break in), and that's not even a particularly expensive set!