As long as we are on the subject, why did the folks down at Android do away with that feature in the first place? I have an old Gingerbread phone, and it's probably the feature I like the most about it, lol. What did they have to gain by not letting us send apps to the SD card anymore if we want to??
It was born in the days when phones had 512 MB or 1 GB *total* storage - and it never worked right.
It was/is a stopgap measure that as Hadron pointed out, couldn't move the entire app.
The more this abomination hangs on the more support issues it creates - made worse by unscrupulous suppliers not above lying about it.
It's really simple - there's a huge security problem putting entire apps and private data on a storage device with inherently lower security.
(Side note follows) I have never had word of the sd card vulnerabilities actually hitting anyone but the large influx of new users read the app permissions, bitched about Android security without getting it and we got the KitKat sd card protection debacle.
Google can't control unscrupulous suppliers and they can't control Android getting jammed onto inadequate hardware. Nevermind that people believe that phones really only suited for Gingerbread can run Lollipop, phone makers just give them specs and lies.
But Google can control architecture, so Android M deals with permissions, private data, and full sd card app support.
And then this stupid nightmare might end.