Not Taking Reservation Yet Despite Sporadic Availabilty? [guest] [Greece]

I like to book far in advance. I found a place that required a request to book for next year. The calendar has sporadic availability. Random days and weeks blocked off with others open. The host responded they don’t take reservations until next year. I understand sometimes they leave it open by mistake but why so many random days booked if they won’t take reservations yet?