This is an essay.
It contains the advice or opinions of one or more Wikipedia contributors. This page is not an encyclopedia article, nor is it one of Wikipedia's policies or guidelines, as it has not been thoroughly vetted by the community. Some essays represent widespread norms; others only represent minority viewpoints.
If you're here, it's probably because your category was up for deletion or renaming at WP:CFD and the Wikiproject you are a member of was not notified of the discussion. Hopefully this essay will help you understand why.
Why didn't you notify my Wikiproject?
Why wasn't your Wikiproject keeping track of its categories? Here's the short version of why I didn't notify: There are hundreds of Wikiprojects, and I do not have the time or resources to a) keep track of all of them, and b) know what categories each Wikiproject is interested in.
But we have these templates dotting the talkpage landscape! That tells you who to notify.
Not always. I've come across many categories that had no talkpage template, I've come across categories that had a template for one wikiproject, but not another. And in all cases, someone would come out of the woodwork yelling at me because I should have known to notify such-and-such wikiproject, even though they didn't have a template on the talk page.
But it's obvious that which Wikiproject to notify
Maybe it's obvious to you. It's not obvious to me, and I'm not going to notify every wikiproject I think may be interested in a category. Because for the bulk of categories, there could be 3 or 4 projects interested.
Does this mean you want to sneak things through without discussion?
Not at all! Believe me, it's better for all when more people join the discussion, and I welcome that. Just because a wikiproject isn't notified doesn't mean nobody is. The requested rename/merge/delete is listed at WP:CFD for minimum seven days, a tag is added to the category itself, and in some cases, someone will usually notify the creator of the category. That said, if nobody shows up to discuss it, then nobody shows up. Do I prefer that? No. But sometimes that happens.
So you do notify people. Why not notify everyone?
If I'm interested in something, I'm going to make damn sure I know about it. For example, if I am interested in a television show, I'm going to make sure I check the listings to find out when it is on. I'm not going to sit back and complain to the cable company because they didn't call me personally to tell me when it would be on and because they didn't, I missed the show. The cable company has gone to reasonable steps to put out the listings, the rest is up to me. It's pretty much the same way here.
So what do I do?
As I asked above, Why wasn't your Wikiproject keeping track of its categories? I know you have watchlisted the articles; that's how you know the category is being removed and is about to be deleted. Just watchlist the category as well, and you'll know when the CFD tag gets added.
Another solution is to follow the example laid out by Hesperian for WP:AUS here.
Who watchlists categories?
I have plenty of categories on my watchlist, and I know of many editors that do also. You can too, it's very easy.
But don't you have to notify us?
There is no policy that states Wikiprojects must be notified. If anything, it is a courtesy, one that would be extended by the person who nominates the category for deletion. When I get involved with the CFD discussion, it is to close it, and notifying you then is pointless. Again, this goes back to the Wikiproject keeping tabs on what it is interested in. I can't say this boldly enough: If a project is interested in a category, add that category to a watchlist.