Versions of uTorrent since 3.0 (the 1st after uTorrent changed hands to new devs) have collectively often had serious limits on
seeding performance, not
leeching performance. In other words, they download fine, but have problems uploading. And yes, that's going to have a noticeable real-world effect on sites that track ratio, such as BakaBT. The most recent version of uTorrent (3.3.2), however, also has serious problems with leeching (gets stuck "finding peers"), rendering it essentially useless.
As to WHY they limit seeding, I highly doubt it's an intended behavior; there's been more than one dire bug introduced since uTorrent was bought out. Some have apparently been very difficult for the new devs to squish. And the troubles 3.3.2 has leeching are quite obviously not on purpose ^^' .
Edit --> Just read their
forums for a bit. A lot of the problems (and lack of solutions, so far) wil become crystal clear. From HD "thrashing"/cache issues, problems with seeds/peers, and so on, it's an eye-opener. Funny, how both 1.8.5 and 2.2.1 do
not share these problems, yet the current devs continually say the problem isn't the software *grumble* -.-' . They most often pass it off as issues with Windows itself.