Quite simply, many others and I hated oxygen swimming. This was not helped by several accidents. It is also worth noting that the phase was weeks long. The advantages of rebreathers are reasonably obvious and include the following. They are quiet.
Military versions are also non-magnetic.
The first is important if you wish to approach fish closely. Both are important if the intended rendezvous is with a mine. They conserve gas and hence allow long endurance. They can be very small and allow wearers to carry considerable other equipment and supplies. I have no doubt that colour and appearance are still the dominant factors in the choice of dive gear for many people.