Why do people like "flashy" champions?

This is not a QQ thread. I know that champions like Yasuo and Zed are balanced, and I never usually have major problems with them. I do think that some flashy champions like Riven and Vayne are unbalanced, but this is not a opinion that is shared by every player.

That said, I would like to know why people like to play "flashy" champions so much. I am specifically referring to these champions:

I would list too, but since the last nerfs, I have seen very few people playing her. But before the nerfs I used to see Nida on almost every of my battles.

What I mean with "flashy champions"?

• Champions that have a lot of mobility
• Champions that either do not have costs to their abilities, or those costs are inconsequential.
• Champions that can snowball really easily, and many of them have a great early game
• Because of those three attributes, they tend to have lots of outplay potential.

They are extremely popular, and I would like to know why. They don't even ensure the victory many times, and on my opinion, they are extremely unfun to play against, either because they have an oppressive early game, or because I have to play perfectly otherwise they snowball out of control.

I would not mind if they were just popular at ranked games, where people try their best to win and there would be a reason for them to play those champions. However, even at normal games, I can't have fun because they are so popular, at least on the server where I play. In fact, at normal draft pick games, I ban those champions not because they are OP, but because they are so frustrating and unfun to play against. Everytime I lose against a for example, I feel that I've been outplayed and the enemy was better than me. But this is not the same when I play against a "flashy" champion. Unless I am using a flashy champion myself (I rarely play them) then I don't feel that I've been outplayed if I lose. Instead I feel that they took advantage of an obnoxious champion.

I feel the lack of playing against unpopular, immobile and forgotten champions like - I really like playing against them because they aren't flashy, I always have a plan to beat them, and if I lose against them, then I don't have to worry whether the enemy was better than me, or if they just took advantage of mechanics that are really frustrating to play against. Why don't people play them more? They can be as fun, if not more fun than "flashy" champions because they actually present a challenge; because they are immobile, you can't just make risky plays like you would do with a flashy champion. You actually have to think and plan everything that you want to do.