These reasons are pretty much why.
- encounter rates of some Pokes (For example you encounter a thousand Tentacools while you're surfing)
- the odds of finding a shiny (It's too low)
- some of my faves are too rare or hard to find
- safari zone (I just hate the concept)
- Evil organizations using weak Pokes (Like Team Rocket for example. I mean, who in their right mind use too many Rattatas?)
- Trainers NOT evolving their Pokemon (Sometimes, I can't train right because of this)
- Event Pokemon (Although it doesn't matter to me anymore, how can we "Catch 'em all" when these happen and seriously, I think Gamefreak is waaay to biased)
- some fans focusing so much on the negative (Seriously, unless it's being asked like in this topic, keep your opinions to yourselves)
- biased fans (I dunno why so many fans have so much biases towards certain Pokes or characters, or themselves. I undertand you like them but...)
But these shouldn't matter to me anymore. Pokemon is about being enjoyed, no matter what we have. Let's not get ourselves too immersed and not make this our life as there are more important things.