Yep target practice. There's different types. There's obviously your, slow, precise target practice focusing on tight groupings and hitting the target where you want to hit it however there are a bunch of other more specialised drills for training reaction speed and ability to actually perform at a moments notice.

While your initial drills start out using relatively few rounds at a time, more complex/difficult drills involve far more rounds, often requiring multiple magazines and multiple targets. These types of drills are generally aren't done at your basic indoor shooting galley ranges but even there there are plenty of ways to burn through a substantial amount of ammunition.

And while part of it is that in general shooting as a hobby is fun, another part is that some types of drills just require a lot of ammunition. ex: malfunction clearing drills where there are non-functional rounds mixed in to your magazines and you need to perform your drills with as little time loss compared to normal as possible. i.e. knowing how to react when things go wrong under pressure.

And so a single range day can easily put someone through tens of magazines which quickly gets into the hundreds of rounds. Then assuming you are going to the range weekly, biweekly, or monthly, that puts you into thousands or even tens of thousands of rounds per year.