There is always a risk with surgery. I've had several go through their neuter without issue, I've also had one die and another almost die. So it can happen.
With reproductive cancer not being a big risk for male rabbits, there are two other main reasons to neuter male rabbits. If they are exhibiting unwanted hormonal behaviors such as spraying, humping, marking territory/not using litter box well, or aggression from sexual frustration. Unneutered males can also be a bit musky. The other reason is if there are plans to bond him with another rabbit. If a rabbit didn't have hormonal behaviors that are bothering me, used the litter box well, and I didn't have plans to bond him with another rabbit, I probably wouldn't risk neutering. Especially if this was a bun that I was particularly attached to.