Or they probably think there's no need to change anything for now because they're still hoping that demand for block space will come back? Do they actually believe that fees under 1 sat/VB is merely a temporary matter?
Plus we can't blame the miners if they don't want the fees to go down to lower rates. They would go out of business, and mining would centralize towards the more efficient and well-capitalized miners.
I believe they do not want to encourage other people to send transactions lower than 1 sat/vB. A lot of people, and wallets, use mempool.space API to calculate transaction fees. 
If they add such feature, it is very likely that fees will drop even more.
That would be bad indeed. There's a debate happening that miners actually need more profit margins counted in sats rather than profit margins counted in U.S. Dollars. What's your opinion about it?
I believe that miners should be counting them in fiat because their expenses ARE in fiat. It would not make sense to count them in units of Bitcoin if real world bills are denominated in fiat, no?