I'd have to agree with the above posts.
Having worked in a rescue for quite a while, it was always the pairs or groups of bunnies that were overlooked. Often people came in to find their existing bunny a friend when they had found out that it was better to keep more than one or when their existing bun was bereaved.
People coming to rabbits for the first time are less likely to go to a rescue in the first place, therefore it's unlikely that the pairs will go out as often. (Having said that when I was new to rabbits I adopted a pair and then my second adoption was also a pair, and then the third - you get the idea).
The problem with getting a single bun and then trying to bond is that your bunny will decide if and when they want to accept a friend and it can take a long time before it gets sorted. You would also then need to rely on a rescue with some experience to bond for you because if you just get another rabbit and hope it works out, you could end up with two bunnies that don't like each other, and then you'd need to find two more friends, not just one.
If you can take a pair, you will see what their personalities are like together, which has to be a plus, and you will be making a massive difference to their lives.
Helen