There are many health and behavioural reasons for neutering and unless there are medical reasons why it can't be done then all rabbits should be neutered.
Females are particularly prone to uterine cancer and spaying them protects them from this. A staggering statistic suggests that 85% of females over the age of 3years develop uterine cancer. Male rabbits can also develop testicular cancer, it less common but no less deadly.
One of the biggest problems we see as a rescue is unwanted litters. Rabbits breed prolifically and two rabbits can soon become 20 on a very short period of time. This is stressful for the rabbits, stressful for the owners and ultimately puts unnecessary strain on rescue centres who are often asked to take all of the unwanted rabbits.
Neutering calms the hormones, rabbits become less territorial and aggressive and stops urine spraying - both males and females can do this! With hormones reduced and agressive behaviour reduced, rabbits can be introduced to other rabbits so they can form a companion bond, which is something every rabbit should be offered. We would not recommend introducing un-neutered rabbits as this has the potential to lead to the rabbits harming each other.
In addition to calming behaviour for bonding, neutering usually resolves many behaviours that humans find challenging. Biting, scratching, lunging, grunting and destroying property can all be signs of a frustrated entire rabbit.