@Richard600 I don't know why, but I find it interesting to ponder. Have they been frequent Airbnb travelers? Are we all getting review-weary? Maybe it's something about the new review process that guests have to go through, which was discussed here recently - they now have something like 12 screens to get through. It still only takes a minute or so - I stayed at an Airbnb in London last week and left a review - but some people might not want to bother. Anyway, food for thought - and no, there is not a limit to how many reviews you can get!
Also, I've saved your listing - it looks so peaceful and away-from-it-all! I'm terrible at geography and have literally no idea where in the world it is, but that doesn't stop me from wanting to go there. 🙂
@Richard600 44 reviews from 49 stays is pretty impressive! I wouldn't worry too much about the last five not reviewing, you only need 50% of your guests to review for superhost status. Although the new review process might be putting some guests off as @Branka-and-Silvia0 & @Ann72 mentioned. I stayed as a guest last month and was shocked at how long and convoluted the review process was for guests compared to what hosts do. And compared to the reviews for booking.com and tripadvisor that I've done as a guest it seems like massive overkill (or data mining...)