creating arrays withing families can be difficult to make and constrain, and because that tool create groups they also perform really poorly.
however Revit already has a tool for repeating elements thats works really well, the repeating detail tool.
if we could use the same tool with model elements in the standard family environment we could make lighter, more efficient families that are also more robust.
for example the repeating detail tool can handle 1 object where the array requires at least 2.
there are many reasons why we needto array nested componants in familiys, like louvre windows or batten screens and on large projects these elements significantly slow down the file.