Sony is far more reliant on PlayStation to keep the company profitable than Microsoft is on Xbox, and have far less cash in the bank.
Sony could definitely take some losses if they saw a potential for profit after a period of time, but they don't currently have a business model that would make that a viable option. If they made a loss over the course of the PS5 gen, where are they likely to make it up from in the next gen?
Microsoft is all in on a business model which could provide huge amounts of recurring revenue, entirely divorced from needing to make and sell hardware, but which could take a very long time to become profitable, but they also have the size and cash reserves to take those losses for a long time to reach that point.
Sony's business model is based on selling hardware and then profiting from sales and subs on their platform. If their platform doesn't make a profit for an entire gen, they will find it difficult to sustain themselves until a point where they do reach profitability.