Those sales would only hurt the platform and not the developer right? Cause they would still make money
If it hurts the platform, it directly hurts the developers under the roof of these platform holders (SCE, Nintendo, Microsoft), the devs rely on the sales on those exclusives. If they were also brought to PC, a big chunk of the sales would move to the PC and the results of these sales would mostly go to the Publisher/Platform holder instead of the devs because they have to deal with the logistics of working with a different ecosystem and economy. Hence, if you add the PC sales, the Platform holders would take bigger chunk of the profits to balance the cost of working with, like I said, another ecosystem. Therefore, taking away some of the profits a dev team/studio would usually make.
To make this clear, a console exclusive is guaranteed-money (not counting the sales of the games on long periods) for the development teams. Although, for a platform holder, when working as the publisher of said team, that usually ''guaranteed-money'' would be greatly impacted due to the PC sales, lowering their profits of said teams (first-party studios).