>>83711643Essentially, when single issues don't sell well, or as well as might be expected/hoped, they don't always get collected into trades. There's a fixed cost to printing and distribution costs - and it also depends on what the return policy will be for the distributor and the LCS, so that a certain number of copies need to be printed (and, of course hopefully also sold) to make the project worthwhile.
Just because, for example, ten issues of any one title came out before it got cancelled don't expect there to be a collected trade. In fact, trades will get solicited and then never actually come out, it happens especially to low selling titles or titles where they did one trade for the first arc of 5-7 issues and the trade also didn't sell well.