Not sure why other airlines don’t have this same function on their website? On Emirates.com you can see your tier miles month by month for upcoming travel, and whether you would requalify for your current tier during the rolling tier period.
You can go back and forth to see how many tier miles you have earned in the past, and will earn in the future. It won’t, however, show how many redeemable miles you will earn from the flights.
This feature is very useful and would be beneficial if other airlines would implement it as well.