That's because our dear leaders have rationalized that because they are unable to source enough vaccines to double dose everybody within the recommended time frame, it's better to give more people a single dose and move the second shot further out.
I think it's a case of them listening to the experts that told them what they wanted to hear to support their plan. Personally, I think it's important to get more people fully protected with both shots rather than run the risk of spreading them so far apart, but I am no expert, and I have not even stayed at a Holliday Inn lately.