Wasn’t it so that you could wreck them with foot archers? Even if they can’t fire further (don’t remember if that was the case) having foot archer vs horse archer shootout was always really costly exchange for the horsey bois.
And it takes a lot of time to train soldiers to effectively ride horses, shoot bows and especially to ride horses while shooting bows while also making sure there’s enough money/logistics to take care of those troops. Much easier to give tons of people a simple bow and tell them to have at it. Or spears. Just… spears for everyone.
I think playing with them can be fun. And done right they usually have some counter. For example, foot archers being able to fire further than the horse archers so ample enough of foot archers should be able to cause them problems.
Another stupid form of this is when they level up with you. The bandits sudddenly have armor made of daedra foreskins wielding flaming dragon bone swords and are level 9 gazillion.
Both ruin the immersion but it’s easier for me to justify bandits being fucked in the head than it is justifying them having turbo rare shit all of a sudden.