Our place hosts up to 14 guests with different bed configurations available, preparation required, etc.
Instant book simply wouldn't work for us, and would likely hit our ratings in a big way, with no real benefit.
For the kind of groups that would be interested in a larger place, my experience is they are usually willing to take the time to request, and even do a little inquiring of their own.
So I try to achieve high search placement by quick responses, trying to maintain high reviews, and perhaps riding on superhost status, to overcome my not having instant book enabled!
Instant book is unlikely to ever work for us!