There used to be night shelters available all year round, fully staffed and working on a ‘first come first served’ basis. You would see the queues forming from the afternoon. But then the housing stock was sold off still further (I’m thinking in my own area of a large block of flats, owned by the council and used for emergency single homeless accommodation - sold to a private company which promptly converted them into luxury flats for the private market - oh the irony).
Then access to the emergency night shelters had to be strictly controlled, no more queuing round the block, referral from other agencies only (usually social services emergency duty teams). Vulnerable homeless people are not likely to be able to either self refer or contact agencies, so that kept the referral rates low, but the most vulnerable remained on the streets, and so on.
Proper housing provision, including emergency shelters costs money. Successive governments have decided social housing is not a priority. It’s that simple I’m afraid.