We do sometimes, but the official stance is that it’s reserved for exceptional circumstances. The reason for this is fairly simple; if we stickied every available topic du jour, it’d take up half the forum.
For instance, there’s an argument for stickying celebrity RIP threads (because whenever someone famous dies there’s a flurry of activity as everyone races to be the first to create a thread without reading the forum first, and then we spend half the day closing duplicate threads). But if we’d done that in 2016 it’d have run off the first page.
If you’re posting a new thread, it should be blatantly obvious whether or not there’s a chance someone else is likely to do so as well (deaths, imminent cycling events = likely, how do I fix my washing machine = less likely) and it should only take a moment to read the forum index to see if it’s been done (though granted people’s choice of thread titles doesn’t always help).
If duplicates happen please report them and we’ll sack them off (and it’d be really really helpful if you included the URL to the other thread too, please).