Seems like they are pre-installing the major hardware to make installation easier for the service technicians later after the tub has been delivered. Some spa brands require you to choose before delivery if you want the speaker package or not.
My Highlife came from the factory with two cutouts for the speakers capped off with covers. Installation is *relatively* easy to install speakers once you have the hardware/electronics to wire up to the system and then enable from the service menu. There isn't any cutting or modifications to the shell needed to install the speakers.
I actually found a handy video online showing me how to install the popup speakers for my spa, although I had trouble locating instructions for installing the subwoofer unit, so I opted to simply pay my dealer to install speakers rather than risk voiding any part of my warranty on the investment. So far I'm very happy with the sound system, worth the money so far.