There have been a lot of arguments in the guitar-making world about traditional neck joins vs bolt-ons and I think bolt-ons are much more accepted now especially since Taylor started doing them. I know a Spanish guitar maker who swears by bolt-on necks even though he was taught the good old Spanish method. From speaking to him I believe they are more stable in the long-term not to mention easier to deal with for repairs. I have a number of guitars/ukes with bolt-on necks. My Cleveland bass has a bolt-on neck and apart from being fantastic for travel I can't tell any difference compared to previous basses I've owned made with traditionally-joined necks.
Going off of what Adiran says. From what I understand bolt on becks can help a basses sound by allowing the neck to vibrate more freely, while also remaining stable. There are other upsides as well, if there is an issue with the top of the instrument, and the luthier couldn't access it, they would have an easier time. If a neck were to break, the repair would be a ton easier, since the joint could be made to be interchangeable.
The issues I have with removable necks
- The hardware, will it rust/oxidize, will it buzz, and will I have to worry about it (Is it built for longevity) CF instead of metal?
- What's the best way to hide the procedure, a removable dowel?
- What if I don't want to travel, and I want something more permanent with a glueless joint?
- Who does the best job?