[Tomte]

Because you need to come up with a design for the cursive variant and then draw all those glyphs.

So the time needed is probably shorter than the time spent on the regular variant, but only by a small factor, certainly not orders of magnitude.

[sp332]

The glyphs can look completely different in italic. http://www.fffranziska.com/#sec_italics And after drawing the glyphs, manually checking and adjusting the kerning between every pair of glyphs takes a lot of time too.

[lucianp]

You are right. From reading the comments on the issue [2], this seems to be the reason why it takes so long. Although I have now idea of how fonts are made, I think the work needs to be done for all currently available weights (7 different weights).