To offer another look on the issue - Neil Gaiman explained in an interview with Chip Kidd that there was also the concern for continuity with other DC comics. It turns out that in the issue where Dr. Dee escapes from Arkham Asylim, it was supposed to be the Joker, rather than Scarecrow. 

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However, Gaiman was told that Joker had just died in another comic, so he couldn't appear in _The Sandman_. Gaiman explains that he ran into similar problems multiple times (in _The Wake_, Superman was originally to have his cape stick out of his cloak, and constantly look back at it afraid, it would expose him), and the issues - having to synchronise the continuity of _The Sandman_ with another comic, and having to approve it - was too much hassle.

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This is the interview (the relevant portion starts at 57:32):

https://youtu.be/0ei9OQkQ2BU?t=57m32s


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