Thank you Wyntre for being reasonable and saying what I wanted to say, except I would have been sarcastic and rude and condescending. I'm pretty bad about that.
Anime series that begin before their manga is finished, and then either have to have long segments of filler to buy time, or end way before closure can be achieved. (Rurouni Kenshin and Fruits Basket are two of my favorite anime, but I REALLY wish that their respective animating companies would have waited a year or two to make them so that they could have finished properly.)
But that isn't feasible, and this has been discussed quite a few times on here. Companies want to make an anime series while the manga is popular. This results in the anime running concurrently with the manga, because they know they'll get viewers. And since you can fit more into a 22 minute anime episode than you can in a 20 page manga chapter, the anime is going to catch up to the manga fast. Again, since the purpose of the anime is to draw in viewers of the already popular series, this leaves them with two choices:
1. Create filler episodes to buy time until more chapters of the manga can be produced...this is what Bleach and Naruto do. This is the easier of the two options; self-contained stories can usually be done pretty well (except when they turn out to contradict canon accidentally, like the Warship Island arc in One Piece did where Zoro said "Sure I can cut steel chains no problem!" but then later in the series facing off against Mr. 1, stated that his swords couldn't cut steel). Still, there's usually enough secondary/tertiary characters that can be played around with and have absolutely no bearing on the plot, like the filler episodes of Bleach that focus on that spirit hunter guy (forgot his name).
2. This is the harder option, the one that Full Metal Alchemist and Fruits Basket did, is to just say "Well okay now we're just going to ignore the manga and make up our own storyline." This has the added benefit of being something new and different from the manga storyline, instead of just seeing the same thing you read. The downside of course is that usually the anime storyline is horribly inferior.
Again, these are really the only two options...there is technically a third option which would be "End the anime completely and then make an entirely new series later." Naruto did this to an extent with Shippuden, but that's more or less an exception, and besides it's not like the Naruto manga was ending anytime soon. Because, as I said, companies want the anime to run at the same time as the manga. Is this a good plan? It has its ups and downs, but it's how they've done it and how they'll always do it.
And as far as I know Kenshin's ending was kind of because of this? They were trying to make filler to buy time for the manga to continue, but the filler was so bad that the ratings died and they just ended it...at least, that's my understanding of it (I could be wrong). Same thing with Naruto and the whole "filler hell" thing they had going on.
and then there's even worse 
WayaxIsumi? KimihroxKaga? HIKARUXSAI?!?!?!?!? GROSS! What happened to Hikarux
:lol:
