Kind of a weird analogy but I feel like goalies are "illiquid assets" like a house, whereas forward are "liquid assets" like a stock. You don't just sell your house cause someone offers 5-10% over the market price. If you do that you will uproot your life, won't necessarily find a house in the neighborhood you want, and you'd have to then offer at least 10% over asking or more to get that house you want so you might come out behind anyway. You only sell your house when you're ready to upgrade, or when you have two or more houses and can't afford upkeep on both of them and need to cash out.
(This is also true of the star/core players on your team, partially why so many fantasy trade proposals involving stars are a complete waste of time)
This is why the trade for a goalie this offseason is going to hurt, especially cause it is very very much a seller's market now. Additionally I think a lot of GMs saw what Detroit/Buffalo/Montreal did this year and broke camp with 3 goalies and will copy them. I expect the goalie trade to hurt unless Fitz goes cheap again with a question mark guy, or adds two question mark guys.