FPS games are one of the most popular game genres in the modern world, and since the early days of Doom they have frequently dominated both the gaming scene and gaming competition. In more recent years, popular first person shooting games such as Team Fortress (original) and Counter Strike 1.6 significantly increased the popularity of the genre. In later years, CS:GO and Call of Duty launched onto the scene and made a huge impact by bringing eSports into the front running line. Finally, in more recent history, the huge surge in popularity of games like Fortnite and Player Unknown Battlegrounds (PUBG) launched the "Battle Royale" niche of games and with it finally brought casual first person shooting games to the masses on both mobile, console, and desktop.
A huge number of games however have historically had issues with various game cheats such as aimbots and wallhacks. Every time a game is created it is only a short amount of time until cheaters on the other side create the code for a game cheat, and with the huge popularity of shooting games it's no wonder that a huge number of these coders turned their attention to FPS games. As such, with every new game released it is only a matter of time before you are able to find aimbots, wallhacks, ESP, and various other cheats included.
With shooting games specifically, the reason for this is clear. When we compare FPS games to other majorly popular games like MMORPG or RTS, the advantage is much more mechanical than it is strategic. Whereas in real time strategy games, there is far more importance placed towards the overall strategy, and in massively multiplayer online roleplaying games you'll find that the majority of the advantage is put towards "grinding" on the game to level up your character. When it comes to FPS games though, almost all of the game is based exclusively on the mechanics of aiming and shooting your enemies. As such, aimbots which automatically aim and kill enemies for you give you a dramatically huge advantage over your enemies.
This means that with the right cheats in a first person shooter, even a bad player can almost instantly win every single game - this makes the use of cheats in FPS games very very appealing to potential cheaters and has lead to a huge boom in the number of cheats utilized in online gaming. Combine this with many games shifting into a free-to-play format (for example, like Fortnite) and you'll have a combination which leads to a cheating boom. This has lead to a huge popularity in fortnite aimbots which have exploded in popularity and even lead Fortnite game creator Epic Games to threaten to sue aimbot and cheat creators by giving an unfair advantage and "creating a competing product".
Whatever your view on aimbots and other game cheats though, they have an established place in the modern world of gaming and have existed for as long as first person shooting games have. In many people's eyes, since shooting games cater to a far more relaxed game environment than other professional eSports games, this means that using these cheats for fun in casual gaming is "fair game". If you compare a game like Call of Duty with a hyper competitive game like Starcraft then you'll find a completely different ballgame in the level of competition amongst the gamers. This isn't to diminish the efforts of eSports gamers who play to a high level in shooters but only to illustrate that there is a profound difference between those using cheats in casual games and those using cheats in the more serious games.