Ordinary users become a target of DDoS way more often than you would think. These days it tends to be related to competitive multiplayer video games, but I'm sure there's still some IRC drama and small-time Minecraft hosting driving it.
In general it's extremely unlikely unless you are engaging in "high risk behavior," but at the scale of an ISP there are enough users doing that kind of thing (Twitch streaming, etc) that it becomes an appreciable frustration for your network operations.
> These days it tends to be related to competitive multiplayer video games, but I'm sure there's still some IRC drama and small-time Minecraft hosting driving it.
This sounds like the sort of thing with similar prevalence to things like running a Tor node. This might even be an example the other way, when your game server or what have you has thousands of peer connections and this thing breaks it by misinterprets that as a denial of service too.
In general it's extremely unlikely unless you are engaging in "high risk behavior," but at the scale of an ISP there are enough users doing that kind of thing (Twitch streaming, etc) that it becomes an appreciable frustration for your network operations.