Kender have a bad reputation because of players who make Tas clones, just like drow get bad rep because of Drizzt clones.
Really, not all kender are innocent crazy kleptomaniacs. You have to remember that most of the kender in the stories have been young and inexperienced. Rarely do we get to see the mature experienced ones whose wonderlust is fading and who have learned self-control. The kender from the excellent novel Spirit of the Wind should be the poster models for the race, not the eternally childish Tas. There we have kender who refrain from pickpocketing everything, who understand their own actions, and who aren't goofy all the time.