You've already identified the fact that being equally proficient with both hands gives you some redundancy in case of injury although there are plenty of other potential injuries or illnesses which could hamper you working so I'm not sure that is a very compelling reason.

Perhaps a better reason is that it potentially offers more versatility in your technique and there may well be circumstances where working right to left as opposes to left to right is an advantage.

Similarly trying to draw with both hands my free up your technique a bit and help you develop more of a personal and expressive style as well as forcing you to focus more on the subject and less on the mechanical process or reproducing an image.

You've already identified the fact that being equally proficient with both hands gives you some redundancy in case of injury although there are plenty of other potential injuries or illnesses which could hamper you working so I'm not sure that is a very compelling reason.

Perhaps a better reason is that it potentially offers more versatility in your technique and there may well be circumstances where working right to left as opposed to left to right is an advantage.

Similarly trying to draw with both hands my free up your technique a bit and help you develop more of a personal and expressive style as well as forcing you to focus more on the subject and less on the mechanical process of reproducing an image.