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 (in #5, "Passengers"), it was supposed to be the Joker, rather than Scarecrow.

_{Click for full resolution}

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.

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

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 (in #5, "Passengers"), it was supposed to be the Joker, and his April Fool's joke (hanging himself), rather than Scarecrow.

_{Click for full resolution}

However, Gaiman was told that Joker had just died in another comic, so he couldn't appear in The Sandman. In this light, Scarecrow saying

If you see the Joker, tell him to hurry back. It isn't April Fool's Day without his little jokes...

gains another meaning (we that @Shokhet for spotting that interpretation). 

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.

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

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.

_{Click for full resolution}

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.

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

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 (in #5, "Passengers"), it was supposed to be the Joker, rather than Scarecrow.

_{Click for full resolution}

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.

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