~No idea about baseball but a tragedy usually forces changes. In cricket body line and leg side field restrictions were implemented for safety reasons and according to reports 174 players died on the cricket field in the past 100 years and majority of the death were before helmets and safety protections were compulsory.
In baseball the rule came into affect during the early as long as i know and what i heard is that a player died because of spitball and during that time there was no helmet either for baseball and all they need was one death to change the rules, not sure why it took a long time for cricket to change some of the rules as 174 players is a very big list to make any changes.
This is a temporary restriction that is implemented so that cricket could resume during the pandemic and eventually they will allow players to shine the ball using saliva.
Once a rule is implemented it will take a long time to remove that until there is demand from the players to remove the ban.
Cricket is a gentleman's game and unfair means must be banned. If saliva is allowed, then players may ask why sandpaper and Vaseline is not allowed. Now ICC can't specifically ban one of them and allow the other. Either both should be allowed, or all these substances must be banned. And I would prefer the latter. Let these bowlers learn how to swing the ball naturally.
Using sandpaper and Vaseline, then why not a steel bat
. To swing the ball you need to have a shining surface if i am not wrong and how they would do that without polishing the ball, lets start using a bowling machine why injure the bowlers. I consider bowling is a difficult part in cricket than batting, historically batting was difficult because there were no protection.