It comes down to personal choice in brewing.
I went from extract to BIAB to 3V system, back to BIAB and then to an all-in-one.
For my personal brewing style, I like to set up the mash and allow it to proceed while I do other chores around the farm. The 3V system required a bit more attention and clean up than the BIAB. Moving to the AIO system, I traded propane heat for electric and made temperature control much better. Clean up is a little more involved but it is a trade off in being able to set everything up the night before and waking up to hot water ready to dough in. Time was just traded from the beginning of the brew day to the end of the brew day. Since I do basically full volume mashes in my AIO, there is no need for additional vessels. Some people still retain a smaller kettle for heating up sparge water.
For those people who want to be more hands-on in the brewing process, the 3V systems are more appealing.